<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ca039-1148-71f2-bf5e-a7f1690890bc,g:ba2693d9-2af3-47cd-9bef-0ac9c80165fe-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.coremt.com/role/ConsolidatedStatementsofComprehensiveIncomeLoss" xlink:type="simple" xlink:href="cmt-20251231.xsd#ConsolidatedStatementsofComprehensiveIncomeLoss"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/ConsolidatedStatementsofComprehensiveIncomeLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019ca039-12b7-7da8-8dc2-37261f9b897f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019ca039-12b7-7172-bf94-beccbcdda89b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019ca039-12b7-7da8-8dc2-37261f9b897f" xlink:to="loc_us-gaap_StatementTable_019ca039-12b7-7172-bf94-beccbcdda89b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-782e-9b9f-4e71762cf7e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019ca039-12b7-7172-bf94-beccbcdda89b" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-782e-9b9f-4e71762cf7e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-782e-9b9f-4e71762cf7e3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-782e-9b9f-4e71762cf7e3" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-782e-9b9f-4e71762cf7e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-71ba-a00e-6bc2093ee49e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-782e-9b9f-4e71762cf7e3" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-71ba-a00e-6bc2093ee49e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019ca039-12b7-7c33-8b7f-1afc8bf53c7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-71ba-a00e-6bc2093ee49e" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019ca039-12b7-7c33-8b7f-1afc8bf53c7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019ca039-12b7-7b64-b730-64d62d3517a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-71ba-a00e-6bc2093ee49e" xlink:to="loc_us-gaap_InterestRateSwapMember_019ca039-12b7-7b64-b730-64d62d3517a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ca039-12b7-7733-8519-5170b436b6dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019ca039-12b7-7da8-8dc2-37261f9b897f" xlink:to="loc_us-gaap_NetIncomeLoss_019ca039-12b7-7733-8519-5170b436b6dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParentAbstract_019ca039-12b7-7346-bbff-6d0989c652d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019ca039-12b7-7da8-8dc2-37261f9b897f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParentAbstract_019ca039-12b7-7346-bbff-6d0989c652d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyDerivativesAbstract_019ca039-12b7-727f-b3b3-03559713d488" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyDerivativesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParentAbstract_019ca039-12b7-7346-bbff-6d0989c652d0" xlink:to="loc_us-gaap_ForeignCurrencyDerivativesAbstract_019ca039-12b7-727f-b3b3-03559713d488" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax_019ca039-12b7-7c23-96a2-0c0732a451c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ForeignCurrencyDerivativesAbstract_019ca039-12b7-727f-b3b3-03559713d488" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax_019ca039-12b7-7c23-96a2-0c0732a451c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax_019ca039-12b7-7663-bdfe-7d04d13cf7c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ForeignCurrencyDerivativesAbstract_019ca039-12b7-727f-b3b3-03559713d488" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax_019ca039-12b7-7663-bdfe-7d04d13cf7c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_019ca039-12b7-7a86-9052-434263f72d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParentAbstract_019ca039-12b7-7346-bbff-6d0989c652d0" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_019ca039-12b7-7a86-9052-434263f72d5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_019ca039-12b7-7ea2-a44e-9cac98c825ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_019ca039-12b7-7a86-9052-434263f72d5b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_019ca039-12b7-7ea2-a44e-9cac98c825ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax_019ca039-12b7-70de-8222-32a5415c7495" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_019ca039-12b7-7a86-9052-434263f72d5b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax_019ca039-12b7-70de-8222-32a5415c7495" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_019ca039-12b7-7dc1-a73d-c8f2ba8ce34f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_019ca039-12b7-7a86-9052-434263f72d5b" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_019ca039-12b7-7dc1-a73d-c8f2ba8ce34f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019ca039-12b7-7caf-988b-11465eb21184" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019ca039-12b7-7da8-8dc2-37261f9b897f" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_019ca039-12b7-7caf-988b-11465eb21184" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/ConsolidatedStatementofStockholdersEquity" xlink:type="simple" xlink:href="cmt-20251231.xsd#ConsolidatedStatementofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/ConsolidatedStatementofStockholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019ca039-12b7-7361-a694-0bfa621e4efb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019ca039-12b7-7ebb-ba7c-105e6fe5dff2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019ca039-12b7-7361-a694-0bfa621e4efb" xlink:to="loc_us-gaap_StatementTable_019ca039-12b7-7ebb-ba7c-105e6fe5dff2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019ca039-12b7-7c4c-8813-568f8829b84b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019ca039-12b7-7ebb-ba7c-105e6fe5dff2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019ca039-12b7-7c4c-8813-568f8829b84b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7c4c-8813-568f8829b84b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ca039-12b7-7c4c-8813-568f8829b84b" xlink:to="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7c4c-8813-568f8829b84b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ca039-12b7-7c4c-8813-568f8829b84b" xlink:to="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019ca039-12b7-7c5b-a2e3-ca7880c70d0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:to="loc_us-gaap_CommonStockMember_019ca039-12b7-7c5b-a2e3-ca7880c70d0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019ca039-12b7-7c97-a28c-a73668a65f0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019ca039-12b7-7c97-a28c-a73668a65f0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019ca039-12b7-727f-bfe6-7516ef317d42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019ca039-12b7-727f-bfe6-7516ef317d42" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019ca039-12b7-7d67-99cd-cb973b24697e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:to="loc_us-gaap_RetainedEarningsMember_019ca039-12b7-7d67-99cd-cb973b24697e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019ca039-12b7-72f3-9b46-4bd205f25e67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-12b7-7572-990d-c8d5171953f7" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019ca039-12b7-72f3-9b46-4bd205f25e67" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-73e1-9c5d-c3c0adbdf67a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019ca039-12b7-7ebb-ba7c-105e6fe5dff2" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-73e1-9c5d-c3c0adbdf67a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-73e1-9c5d-c3c0adbdf67a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-73e1-9c5d-c3c0adbdf67a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-73e1-9c5d-c3c0adbdf67a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-7a0a-a251-5ea8948eda8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-73e1-9c5d-c3c0adbdf67a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-7a0a-a251-5ea8948eda8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019ca039-12b7-75bf-a5d1-883b9f71d9b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-7a0a-a251-5ea8948eda8d" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019ca039-12b7-75bf-a5d1-883b9f71d9b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019ca039-12b7-7c89-b131-e34c5fe24502" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-7a0a-a251-5ea8948eda8d" xlink:to="loc_us-gaap_InterestRateSwapMember_019ca039-12b7-7c89-b131-e34c5fe24502" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019ca039-12b7-7361-a694-0bfa621e4efb" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_019ca039-12b7-7ad1-abed-39d74d349136" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_SharesOutstanding_019ca039-12b7-7ad1-abed-39d74d349136" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ca039-12b7-710c-aa56-915f4702745c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_StockholdersEquity_019ca039-12b7-710c-aa56-915f4702745c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ca039-12b7-7326-98ad-9d1cf597336c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_NetIncomeLoss_019ca039-12b7-7326-98ad-9d1cf597336c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019ca039-12b7-7ff2-8502-70735b43d3aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019ca039-12b7-7ff2-8502-70735b43d3aa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019ca039-12b7-7bd2-bc96-5957377bd617" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019ca039-12b7-7bd2-bc96-5957377bd617" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019ca039-12b7-7da0-9e03-8d6d1307bd26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019ca039-12b7-7da0-9e03-8d6d1307bd26" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019ca039-12b7-714d-a561-8ba2608f1e7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019ca039-12b7-714d-a561-8ba2608f1e7f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019ca039-12b7-7f52-9e2e-1b9bb8eae80a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019ca039-12b7-7f52-9e2e-1b9bb8eae80a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_019ca039-12b7-7fba-a6a2-a2944df7541c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_019ca039-12b7-7fba-a6a2-a2944df7541c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_019ca039-12b7-7f84-9fb5-4dc25f1cbbd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_019ca039-12b7-7f84-9fb5-4dc25f1cbbd5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019ca039-12b7-7e89-90f5-768494a336b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019ca039-12b7-7e89-90f5-768494a336b2" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_APICShareBasedPaymentArrangementDecreaseForUnvestedEquityAwardsReclassifiedToLiabilityAccounting_019cb994-e94f-73b6-b36d-5b000a12c53f" xlink:href="cmt-20251231.xsd#cmt_APICShareBasedPaymentArrangementDecreaseForUnvestedEquityAwardsReclassifiedToLiabilityAccounting"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_cmt_APICShareBasedPaymentArrangementDecreaseForUnvestedEquityAwardsReclassifiedToLiabilityAccounting_019cb994-e94f-73b6-b36d-5b000a12c53f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax_019ca039-12b7-70f2-b110-e900a9e952a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax_019ca039-12b7-70f2-b110-e900a9e952a3" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueOther_019ca039-12b7-7c3d-b188-e41dde844c4e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueOther_019ca039-12b7-7c3d-b188-e41dde844c4e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_019ca039-12b7-70ce-a1f2-9972c2fe1c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ca039-12b7-7835-abb0-c74412dcae8c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_019ca039-12b7-70ce-a1f2-9972c2fe1c4d" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_019ca039-12b7-79dd-9c75-974fb2384ace" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ca039-12b7-7cac-ac79-8d5ba646333b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/ConsolidatedStatementofStockholdersEquityParenthetical" xlink:type="simple" xlink:href="cmt-20251231.xsd#ConsolidatedStatementofStockholdersEquityParenthetical"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/ConsolidatedStatementofStockholdersEquityParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019cbe87-c20b-764e-a0fa-949047a9a175" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019cbe87-c20b-7cfc-bb44-8d011b1b2c87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019cbe87-c20b-764e-a0fa-949047a9a175" xlink:to="loc_us-gaap_StatementTable_019cbe87-c20b-7cfc-bb44-8d011b1b2c87" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019cbe87-c20b-72fc-9dfc-2aca970949ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019cbe87-c20b-7cfc-bb44-8d011b1b2c87" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019cbe87-c20b-72fc-9dfc-2aca970949ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019cbe87-c20b-72fc-9dfc-2aca970949ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019cbe87-c20b-72fc-9dfc-2aca970949ba" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019cbe87-c20b-72fc-9dfc-2aca970949ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019cbe87-c20b-751a-941e-6fa44e713eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019cbe87-c20b-72fc-9dfc-2aca970949ba" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019cbe87-c20b-751a-941e-6fa44e713eaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019cbe87-c20b-72d9-896f-1ec2bc4dadf8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019cbe87-c20b-751a-941e-6fa44e713eaf" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019cbe87-c20b-72d9-896f-1ec2bc4dadf8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019cbe87-c20b-7d7a-b6b5-04a7c2de41b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019cbe87-c20b-751a-941e-6fa44e713eaf" xlink:to="loc_us-gaap_InterestRateSwapMember_019cbe87-c20b-7d7a-b6b5-04a7c2de41b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019cbeb3-543d-734d-a5e8-02b55ab60113" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019cbe87-c20b-7cfc-bb44-8d011b1b2c87" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019cbeb3-543d-734d-a5e8-02b55ab60113" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cbeb3-543d-734d-a5e8-02b55ab60113_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019cbeb3-543d-734d-a5e8-02b55ab60113" xlink:to="loc_us-gaap_EquityComponentDomain_019cbeb3-543d-734d-a5e8-02b55ab60113_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cbeb3-543d-774d-9772-0da6a3b53410" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019cbeb3-543d-734d-a5e8-02b55ab60113" xlink:to="loc_us-gaap_EquityComponentDomain_019cbeb3-543d-774d-9772-0da6a3b53410" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019cbeb3-543d-7d88-b370-794741aeda5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cbeb3-543d-774d-9772-0da6a3b53410" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019cbeb3-543d-7d88-b370-794741aeda5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_019cbe87-c20b-7eb6-88a4-b4f15edfe263" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019cbe87-c20b-764e-a0fa-949047a9a175" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_019cbe87-c20b-7eb6-88a4-b4f15edfe263" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax_019cbe87-c20b-7d04-8ec7-36a6441f8050" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019cbe87-c20b-764e-a0fa-949047a9a175" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax_019cbe87-c20b-7d04-8ec7-36a6441f8050" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueOther_019cbeb3-543d-75b4-9bb5-61474ac97c5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019cbe87-c20b-764e-a0fa-949047a9a175" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueOther_019cbeb3-543d-75b4-9bb5-61474ac97c5e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#SummaryofSignificantAccountingPoliciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnusualOrInfrequentItemLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnusualOrInfrequentItemTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-72cf-a310-85432126cac3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-72cf-a310-85432126cac3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-72cf-a310-85432126cac3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-72cf-a310-85432126cac3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-72cf-a310-85432126cac3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-7c1d-9d6f-e4ee5bd52688" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-72cf-a310-85432126cac3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-7c1d-9d6f-e4ee5bd52688" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractBasedIntangibleAssetsMember_019ca039-12b7-7576-9045-e7fcd0a186b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-7c1d-9d6f-e4ee5bd52688" xlink:to="loc_us-gaap_ContractBasedIntangibleAssetsMember_019ca039-12b7-7576-9045-e7fcd0a186b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019ca039-12b7-745f-aee3-dace0063caab" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:to="loc_srt_MajorCustomersAxis_019ca039-12b7-745f-aee3-dace0063caab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-745f-aee3-dace0063caab_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019ca039-12b7-745f-aee3-dace0063caab" xlink:to="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-745f-aee3-dace0063caab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-740f-b60c-c79914deb49e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019ca039-12b7-745f-aee3-dace0063caab" xlink:to="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-740f-b60c-c79914deb49e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_FiveLargestCustomersMember_019ca039-12b7-75f6-8fe4-8c6ae3dbfa4e" xlink:href="cmt-20251231.xsd#cmt_FiveLargestCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-740f-b60c-c79914deb49e" xlink:to="loc_cmt_FiveLargestCustomersMember_019ca039-12b7-75f6-8fe4-8c6ae3dbfa4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019ca039-12b7-727e-aaaf-e68157e7e133" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019ca039-12b7-727e-aaaf-e68157e7e133" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-727e-aaaf-e68157e7e133_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019ca039-12b7-727e-aaaf-e68157e7e133" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-727e-aaaf-e68157e7e133_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-77ee-ba3f-78c06dca3467" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019ca039-12b7-727e-aaaf-e68157e7e133" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-77ee-ba3f-78c06dca3467" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_019ca039-12b7-7606-8c97-3f9da91caefe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-77ee-ba3f-78c06dca3467" xlink:to="loc_us-gaap_SalesRevenueNetMember_019ca039-12b7-7606-8c97-3f9da91caefe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_019ca039-12b7-7fc1-b5cc-3311a8bc1202" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-77ee-ba3f-78c06dca3467" xlink:to="loc_us-gaap_AccountsReceivableMember_019ca039-12b7-7fc1-b5cc-3311a8bc1202" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember_019ca039-12b7-7e08-a317-060473c70633" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019ca039-12b7-77ee-ba3f-78c06dca3467" xlink:to="loc_us-gaap_WorkforceSubjectToCollectiveBargainingArrangementsMember_019ca039-12b7-7e08-a317-060473c70633" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019ca039-12b7-710a-8dd7-2af2c36d14d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019ca039-12b7-710a-8dd7-2af2c36d14d8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019ca039-12b7-710a-8dd7-2af2c36d14d8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019ca039-12b7-710a-8dd7-2af2c36d14d8" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019ca039-12b7-710a-8dd7-2af2c36d14d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019ca039-12b7-7858-94f0-34f8662e5abb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019ca039-12b7-710a-8dd7-2af2c36d14d8" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019ca039-12b7-7858-94f0-34f8662e5abb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_019ca039-12b7-7759-82c1-1127add5ebd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019ca039-12b7-7858-94f0-34f8662e5abb" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_019ca039-12b7-7759-82c1-1127add5ebd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_019ca039-12b7-7343-8728-9375c3831bb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019ca039-12b7-7858-94f0-34f8662e5abb" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_019ca039-12b7-7343-8728-9375c3831bb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019ca039-12b7-76ab-8632-39ad9bc07f80" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_UnusualOrInfrequentItemTable_019ca039-12b7-738f-9721-7b27c707cdc8" xlink:to="loc_srt_StatementGeographicalAxis_019ca039-12b7-76ab-8632-39ad9bc07f80" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-12b7-76ab-8632-39ad9bc07f80_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-12b7-76ab-8632-39ad9bc07f80" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-12b7-76ab-8632-39ad9bc07f80_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7a7d-8ae7-f5e84ee56d30" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-12b7-76ab-8632-39ad9bc07f80" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7a7d-8ae7-f5e84ee56d30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019ca039-12b7-7682-aebf-a74f1da8fb49" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7a7d-8ae7-f5e84ee56d30" xlink:to="loc_country_US_019ca039-12b7-7682-aebf-a74f1da8fb49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019ca039-12b7-734b-9bc3-785fbefc2f4f" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7a7d-8ae7-f5e84ee56d30" xlink:to="loc_country_MX_019ca039-12b7-734b-9bc3-785fbefc2f4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_019ca039-12b7-7b12-87a3-fa0a91f7deeb" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7a7d-8ae7-f5e84ee56d30" xlink:to="loc_country_CA_019ca039-12b7-7b12-87a3-fa0a91f7deeb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_MajorPlantsLocatedInUnitedStatesCanadaAndMexicoMember_019ca039-12b7-719d-a30a-a0398bbdc1fb" xlink:href="cmt-20251231.xsd#cmt_MajorPlantsLocatedInUnitedStatesCanadaAndMexicoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7a7d-8ae7-f5e84ee56d30" xlink:to="loc_cmt_MajorPlantsLocatedInUnitedStatesCanadaAndMexicoMember_019ca039-12b7-719d-a30a-a0398bbdc1fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_NumberOfBanksInWhichCashIsHeld_019ca039-12b7-7711-861b-67080b10ed44" xlink:href="cmt-20251231.xsd#cmt_NumberOfBanksInWhichCashIsHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_cmt_NumberOfBanksInWhichCashIsHeld_019ca039-12b7-7711-861b-67080b10ed44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ca039-12b7-7410-b93e-0103dc427a10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ca039-12b7-7410-b93e-0103dc427a10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019ca039-12b7-7cfa-91c7-d2262eb44c15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019ca039-12b7-7cfa-91c7-d2262eb44c15" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_AccountsReceivableAllowanceForCreditLossChargebacks_019ca039-12b7-711a-a87e-7c410f7a6e1e" xlink:href="cmt-20251231.xsd#cmt_AccountsReceivableAllowanceForCreditLossChargebacks"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_cmt_AccountsReceivableAllowanceForCreditLossChargebacks_019ca039-12b7-711a-a87e-7c410f7a6e1e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryValuationReserves_019ca039-12b7-7647-8834-798156652486" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryValuationReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_InventoryValuationReserves_019ca039-12b7-7647-8834-798156652486" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019ca039-12b7-78b9-8184-41722a59264d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019ca039-12b7-78b9-8184-41722a59264d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019ca039-12b7-72d4-b51b-e986f944d663" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019ca039-12b7-72d4-b51b-e986f944d663" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfIntangibleAssetsFinitelived_019ca039-12b7-7f68-8f27-c1603a07100b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ImpairmentOfIntangibleAssetsFinitelived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_ImpairmentOfIntangibleAssetsFinitelived_019ca039-12b7-7f68-8f27-c1603a07100b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ContractWithCustomerLiabilityIncludingNewContractRevenueRecognized_019ca039-12b7-7ddd-ab8e-ae6ae9b840f1" xlink:href="cmt-20251231.xsd#cmt_ContractWithCustomerLiabilityIncludingNewContractRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_cmt_ContractWithCustomerLiabilityIncludingNewContractRevenueRecognized_019ca039-12b7-7ddd-ab8e-ae6ae9b840f1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_019ca039-12b7-7271-834c-87ca35d42057" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_AssetImpairmentCharges_019ca039-12b7-7271-834c-87ca35d42057" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets1_019ca039-12b7-7e62-bd83-f07561287bb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDispositionOfAssets1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets1_019ca039-12b7-7e62-bd83-f07561287bb6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_019ca039-12b7-7ecb-bd6f-d4993c524d6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_019ca039-12b7-7ecb-bd6f-d4993c524d6d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SelfInsuranceReserve_019ca039-12b7-795a-bf98-014bbe7f8a04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SelfInsuranceReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_SelfInsuranceReserve_019ca039-12b7-795a-bf98-014bbe7f8a04" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PostemploymentBenefitsLiabilityCurrentAndNoncurrent_019ca039-12b7-7ec6-ad1c-d26145b1eb5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PostemploymentBenefitsLiabilityCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_PostemploymentBenefitsLiabilityCurrentAndNoncurrent_019ca039-12b7-7ec6-ad1c-d26145b1eb5b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_NumberOfMajorCustomers_019ca039-12b7-7dd4-a5ca-387c55da3323" xlink:href="cmt-20251231.xsd#cmt_NumberOfMajorCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_cmt_NumberOfMajorCustomers_019ca039-12b7-7dd4-a5ca-387c55da3323" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019ca039-12b7-7e32-b699-0362c11c4431" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019ca039-12b7-7e32-b699-0362c11c4431" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityNumberOfEmployees_019ca039-12b7-7a04-8f6f-d613b33289ea" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityNumberOfEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_dei_EntityNumberOfEmployees_019ca039-12b7-7a04-8f6f-d613b33289ea" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_NumberOfMajorPlantLocationsIncludedInCollectiveBargainingArrangements_019ca039-12b7-7df7-9397-7470bb9e9d0c" xlink:href="cmt-20251231.xsd#cmt_NumberOfMajorPlantLocationsIncludedInCollectiveBargainingArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_cmt_NumberOfMajorPlantLocationsIncludedInCollectiveBargainingArrangements_019ca039-12b7-7df7-9397-7470bb9e9d0c" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019ca039-12b7-7b65-8e88-ba0e8df076f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019ca039-12b7-7b65-8e88-ba0e8df076f0" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax_019ca039-12b7-7c31-8c3e-ce04a4d0c301" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_UnusualOrInfrequentItemLineItems_019ca039-12b7-7623-8ef8-a4f7e85d5d40" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax_019ca039-12b7-7c31-8c3e-ce04a4d0c301" xlink:type="arc" order="19"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/SummaryofSignificantAccountingPoliciesScheduleofPropertyPlantandEquipmentUsefulLivesDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#SummaryofSignificantAccountingPoliciesScheduleofPropertyPlantandEquipmentUsefulLivesDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/SummaryofSignificantAccountingPoliciesScheduleofPropertyPlantandEquipmentUsefulLivesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-70f0-a8b6-02ca0a6edd32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-7987-94a9-a954e1fb0326" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-70f0-a8b6-02ca0a6edd32" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-7987-94a9-a954e1fb0326" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7cef-9b13-5d95467ad2a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-7987-94a9-a954e1fb0326" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7cef-9b13-5d95467ad2a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-7cef-9b13-5d95467ad2a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7cef-9b13-5d95467ad2a0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-7cef-9b13-5d95467ad2a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-71fc-b4b8-d961bd0f01e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7cef-9b13-5d95467ad2a0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-71fc-b4b8-d961bd0f01e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandImprovementsMember_019ca039-12b7-70ce-af75-92641f22892e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-71fc-b4b8-d961bd0f01e9" xlink:to="loc_us-gaap_LandImprovementsMember_019ca039-12b7-70ce-af75-92641f22892e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingAndBuildingImprovementsMember_019ca039-12b7-77b3-b5a2-e58683cf6ff6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BuildingAndBuildingImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-71fc-b4b8-d961bd0f01e9" xlink:to="loc_us-gaap_BuildingAndBuildingImprovementsMember_019ca039-12b7-77b3-b5a2-e58683cf6ff6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_019ca039-12b7-7254-be5c-df3c1d9e6f1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-71fc-b4b8-d961bd0f01e9" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_019ca039-12b7-7254-be5c-df3c1d9e6f1f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ToolsDiesAndMoldsMember_019ca039-12b7-7c41-a17b-52aab3144502" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ToolsDiesAndMoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-71fc-b4b8-d961bd0f01e9" xlink:to="loc_us-gaap_ToolsDiesAndMoldsMember_019ca039-12b7-7c41-a17b-52aab3144502" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ca039-12b7-7c38-a40c-867c97c40b30" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-7987-94a9-a954e1fb0326" xlink:to="loc_srt_RangeAxis_019ca039-12b7-7c38-a40c-867c97c40b30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7c38-a40c-867c97c40b30_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7c38-a40c-867c97c40b30" xlink:to="loc_srt_RangeMember_019ca039-12b7-7c38-a40c-867c97c40b30_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7a7f-9e84-b8307bab0381" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7c38-a40c-867c97c40b30" xlink:to="loc_srt_RangeMember_019ca039-12b7-7a7f-9e84-b8307bab0381" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ca039-12b7-7b84-a133-22f46b1f72a1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7a7f-9e84-b8307bab0381" xlink:to="loc_srt_MinimumMember_019ca039-12b7-7b84-a133-22f46b1f72a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ca039-12b7-777f-9f84-f9bacd42a721" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7a7f-9e84-b8307bab0381" xlink:to="loc_srt_MaximumMember_019ca039-12b7-777f-9f84-f9bacd42a721" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_019ca039-12b7-7118-81dc-66f598377fd3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-70f0-a8b6-02ca0a6edd32" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_019ca039-12b7-7118-81dc-66f598377fd3" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/SummaryofSignificantAccountingPoliciesScheduleOfCollectiveBargainingArrangementsDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#SummaryofSignificantAccountingPoliciesScheduleOfCollectiveBargainingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/SummaryofSignificantAccountingPoliciesScheduleOfCollectiveBargainingArrangementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ScheduleOfCollectiveBargainingArrangementLineItems_019ca039-12b7-71df-9ebc-5ac19a1072b1" xlink:href="cmt-20251231.xsd#cmt_ScheduleOfCollectiveBargainingArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ScheduleOfCollectiveBargainingArrangementTable_019ca039-12b7-7338-9c30-358f7a26045a" xlink:href="cmt-20251231.xsd#cmt_ScheduleOfCollectiveBargainingArrangementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_cmt_ScheduleOfCollectiveBargainingArrangementLineItems_019ca039-12b7-71df-9ebc-5ac19a1072b1" xlink:to="loc_cmt_ScheduleOfCollectiveBargainingArrangementTable_019ca039-12b7-7338-9c30-358f7a26045a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019ca039-12b7-7514-ae4c-8fcd6949c322" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cmt_ScheduleOfCollectiveBargainingArrangementTable_019ca039-12b7-7338-9c30-358f7a26045a" xlink:to="loc_srt_StatementGeographicalAxis_019ca039-12b7-7514-ae4c-8fcd6949c322" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7514-ae4c-8fcd6949c322_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-12b7-7514-ae4c-8fcd6949c322" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7514-ae4c-8fcd6949c322_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-12b7-786d-bf35-5360800b8934" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-12b7-7514-ae4c-8fcd6949c322" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-12b7-786d-bf35-5360800b8934" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019ca039-12b7-7da9-b639-1265366ff831" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-786d-bf35-5360800b8934" xlink:to="loc_country_US_019ca039-12b7-7da9-b639-1265366ff831" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019ca039-12b7-7262-83f6-590689931dac" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-786d-bf35-5360800b8934" xlink:to="loc_country_MX_019ca039-12b7-7262-83f6-590689931dac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_019ca039-12b7-7072-a942-c492df6b8e56" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-786d-bf35-5360800b8934" xlink:to="loc_country_CA_019ca039-12b7-7072-a942-c492df6b8e56" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollectiveBargainingArrangementAxis_019ca039-12b7-78b4-a994-d437340bf094" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollectiveBargainingArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cmt_ScheduleOfCollectiveBargainingArrangementTable_019ca039-12b7-7338-9c30-358f7a26045a" xlink:to="loc_us-gaap_CollectiveBargainingArrangementAxis_019ca039-12b7-78b4-a994-d437340bf094" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-78b4-a994-d437340bf094_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollectiveBargainingArrangementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CollectiveBargainingArrangementAxis_019ca039-12b7-78b4-a994-d437340bf094" xlink:to="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-78b4-a994-d437340bf094_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-761f-9fd8-96729aca2798" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollectiveBargainingArrangementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CollectiveBargainingArrangementAxis_019ca039-12b7-78b4-a994-d437340bf094" xlink:to="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-761f-9fd8-96729aca2798" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_InternationalAssociationOfMachinistsAndAerospaceWorkersMember_019ca039-12b7-7290-a97b-83f5a522fb3e" xlink:href="cmt-20251231.xsd#cmt_InternationalAssociationOfMachinistsAndAerospaceWorkersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-761f-9fd8-96729aca2798" xlink:to="loc_cmt_InternationalAssociationOfMachinistsAndAerospaceWorkersMember_019ca039-12b7-7290-a97b-83f5a522fb3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_SindicatoDeJornelerosYObrerosMember_019ca039-12b7-7c33-8b68-ab5b50f65832" xlink:href="cmt-20251231.xsd#cmt_SindicatoDeJornelerosYObrerosMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-761f-9fd8-96729aca2798" xlink:to="loc_cmt_SindicatoDeJornelerosYObrerosMember_019ca039-12b7-7c33-8b68-ab5b50f65832" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_UnitedFoodAndCommercialWorkersCanadaMember_019ca039-12b7-72f9-bb67-40c79adb4084" xlink:href="cmt-20251231.xsd#cmt_UnitedFoodAndCommercialWorkersCanadaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-761f-9fd8-96729aca2798" xlink:to="loc_cmt_UnitedFoodAndCommercialWorkersCanadaMember_019ca039-12b7-72f9-bb67-40c79adb4084" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_SindicatoDeTrabajadoresDeLaIndustriaMetalicaYDelComercioDelEstadoDeNuevoLeonPresidenteBenitoJuarezGarciaCtmMember_019ca039-12b7-75c4-ab8c-b2a7843d2fa7" xlink:href="cmt-20251231.xsd#cmt_SindicatoDeTrabajadoresDeLaIndustriaMetalicaYDelComercioDelEstadoDeNuevoLeonPresidenteBenitoJuarezGarciaCtmMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollectiveBargainingArrangementDomain_019ca039-12b7-761f-9fd8-96729aca2798" xlink:to="loc_cmt_SindicatoDeTrabajadoresDeLaIndustriaMetalicaYDelComercioDelEstadoDeNuevoLeonPresidenteBenitoJuarezGarciaCtmMember_019ca039-12b7-75c4-ab8c-b2a7843d2fa7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityNumberOfEmployees_019ca039-12b7-7fa5-8234-c4fbe110b959" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityNumberOfEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cmt_ScheduleOfCollectiveBargainingArrangementLineItems_019ca039-12b7-71df-9ebc-5ac19a1072b1" xlink:to="loc_dei_EntityNumberOfEmployees_019ca039-12b7-7fa5-8234-c4fbe110b959" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/NetIncomeperShareofCommonStockDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#NetIncomeperShareofCommonStockDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/NetIncomeperShareofCommonStockDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedLineItems_019ca039-12b7-7f81-ab94-baffc76b262e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDilutedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_019ca039-12b7-727d-8176-b660ed94278d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_019ca039-12b7-7f81-ab94-baffc76b262e" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_019ca039-12b7-727d-8176-b660ed94278d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019ca039-12b7-72dd-ad32-f14e50f92eb1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_019ca039-12b7-727d-8176-b660ed94278d" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019ca039-12b7-72dd-ad32-f14e50f92eb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019ca039-12b7-72dd-ad32-f14e50f92eb1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019ca039-12b7-72dd-ad32-f14e50f92eb1" xlink:to="loc_us-gaap_ClassOfStockDomain_019ca039-12b7-72dd-ad32-f14e50f92eb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019ca039-12b7-7a25-ba81-6cf9802bab47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019ca039-12b7-72dd-ad32-f14e50f92eb1" xlink:to="loc_us-gaap_ClassOfStockDomain_019ca039-12b7-7a25-ba81-6cf9802bab47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ParticipatingSecuritiesMember_019ca039-12b7-76fa-bb15-89f4e50cac13" xlink:href="cmt-20251231.xsd#cmt_ParticipatingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019ca039-12b7-7a25-ba81-6cf9802bab47" xlink:to="loc_cmt_ParticipatingSecuritiesMember_019ca039-12b7-76fa-bb15-89f4e50cac13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedLineItems_019ca039-12b7-7f81-ab94-baffc76b262e" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ca039-12b7-7a62-9c9f-2be6e2b0091d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_NetIncomeLoss_019ca039-12b7-7a62-9c9f-2be6e2b0091d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_019ca039-12b7-7269-b80c-d58e5595e96a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic_019ca039-12b7-7269-b80c-d58e5595e96a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic_019ca039-12b7-7a1e-88eb-a8df635feab6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic_019ca039-12b7-7a1e-88eb-a8df635feab6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019ca039-12b7-753d-9c8e-bdb7cd77c66c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019ca039-12b7-753d-9c8e-bdb7cd77c66c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019ca039-12b7-758e-a325-f17aea82820d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019ca039-12b7-758e-a325-f17aea82820d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019ca039-12b7-7afe-827a-34bb706b4bf2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019ca039-12b7-7afe-827a-34bb706b4bf2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019ca039-12b7-7574-9b64-aec9f364a47d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_EarningsPerShareBasic_019ca039-12b7-7574-9b64-aec9f364a47d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019ca039-12b7-7331-884e-1b511ab6c5b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_019ca039-12b7-7335-a5b9-16dbcdcd99c7" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019ca039-12b7-7331-884e-1b511ab6c5b1" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/MajorCustomersDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#MajorCustomersDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/MajorCustomersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_019ca039-12b7-71eb-9b29-280a21db07bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EntityWideRevenueMajorCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_019ca039-12b7-7043-b988-a99919c19498" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_019ca039-12b7-71eb-9b29-280a21db07bb" xlink:to="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_019ca039-12b7-7043-b988-a99919c19498" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019ca039-12b7-79f5-9c56-d16291ab8e88" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_019ca039-12b7-7043-b988-a99919c19498" xlink:to="loc_srt_MajorCustomersAxis_019ca039-12b7-79f5-9c56-d16291ab8e88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-79f5-9c56-d16291ab8e88_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019ca039-12b7-79f5-9c56-d16291ab8e88" xlink:to="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-79f5-9c56-d16291ab8e88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019ca039-12b7-79f5-9c56-d16291ab8e88" xlink:to="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_BrpIncorporatedMember_019ca039-12b7-760a-955d-670e33318ed9" xlink:href="cmt-20251231.xsd#cmt_BrpIncorporatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:to="loc_cmt_BrpIncorporatedMember_019ca039-12b7-760a-955d-670e33318ed9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_NavistarMember_019ca039-12b7-7bdb-8d03-938848f09ca4" xlink:href="cmt-20251231.xsd#cmt_NavistarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:to="loc_cmt_NavistarMember_019ca039-12b7-7bdb-8d03-938848f09ca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_PaccarMember_019ca039-12b7-7252-b6d0-9a32c00c0f95" xlink:href="cmt-20251231.xsd#cmt_PaccarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:to="loc_cmt_PaccarMember_019ca039-12b7-7252-b6d0-9a32c00c0f95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_UniversalForestProductsMember_019ca039-12b7-736e-89e8-7379adff5a9d" xlink:href="cmt-20251231.xsd#cmt_UniversalForestProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:to="loc_cmt_UniversalForestProductsMember_019ca039-12b7-736e-89e8-7379adff5a9d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_VolvoMember_019ca039-12b7-7b5e-8bdb-90ecd80c33b7" xlink:href="cmt-20251231.xsd#cmt_VolvoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:to="loc_cmt_VolvoMember_019ca039-12b7-7b5e-8bdb-90ecd80c33b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_OtherCustomersMember_019ca039-12b7-76e1-84f3-ded99eb1df17" xlink:href="cmt-20251231.xsd#cmt_OtherCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019ca039-12b7-7ad8-a520-709316295693" xlink:to="loc_cmt_OtherCustomersMember_019ca039-12b7-76e1-84f3-ded99eb1df17" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019ca039-12b7-7e70-8100-1fcbf4abd075" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_019ca039-12b7-7043-b988-a99919c19498" xlink:to="loc_srt_ProductOrServiceAxis_019ca039-12b7-7e70-8100-1fcbf4abd075" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ca039-12b7-7e70-8100-1fcbf4abd075_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019ca039-12b7-7e70-8100-1fcbf4abd075" xlink:to="loc_srt_ProductsAndServicesDomain_019ca039-12b7-7e70-8100-1fcbf4abd075_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ca039-12b7-7430-9e5e-e47819baa515" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019ca039-12b7-7e70-8100-1fcbf4abd075" xlink:to="loc_srt_ProductsAndServicesDomain_019ca039-12b7-7430-9e5e-e47819baa515" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_019ca039-12b7-771d-9f97-2fcf6d622431" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ca039-12b7-7430-9e5e-e47819baa515" xlink:to="loc_us-gaap_ProductMember_019ca039-12b7-771d-9f97-2fcf6d622431" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019ca039-12b7-7ce1-83b8-98ef1b8eeddd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ca039-12b7-7430-9e5e-e47819baa515" xlink:to="loc_us-gaap_ServiceMember_019ca039-12b7-7ce1-83b8-98ef1b8eeddd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_NumberOfMajorCustomers_019ca039-12b7-77f8-8ffe-8707eb29b271" xlink:href="cmt-20251231.xsd#cmt_NumberOfMajorCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_019ca039-12b7-71eb-9b29-280a21db07bb" xlink:to="loc_cmt_NumberOfMajorCustomers_019ca039-12b7-77f8-8ffe-8707eb29b271" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-12b7-71d6-95ed-ff098d69672d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_019ca039-12b7-71eb-9b29-280a21db07bb" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-12b7-71d6-95ed-ff098d69672d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/ForeignOperationsDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#ForeignOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/ForeignOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019ca039-12b7-7f96-8e9f-ff954379ec3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019ca039-12b7-78aa-900a-e627bcfc8e8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019ca039-12b7-7f96-8e9f-ff954379ec3e" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019ca039-12b7-78aa-900a-e627bcfc8e8a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019ca039-12b7-7791-b3f9-58caa607bcac" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019ca039-12b7-78aa-900a-e627bcfc8e8a" xlink:to="loc_srt_StatementGeographicalAxis_019ca039-12b7-7791-b3f9-58caa607bcac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7791-b3f9-58caa607bcac_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-12b7-7791-b3f9-58caa607bcac" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-12b7-7791-b3f9-58caa607bcac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-12b7-75d2-ab56-8ec48885a52a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-12b7-7791-b3f9-58caa607bcac" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-12b7-75d2-ab56-8ec48885a52a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019ca039-12b7-7fa8-b075-09a9fa0c64c1" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-75d2-ab56-8ec48885a52a" xlink:to="loc_country_US_019ca039-12b7-7fa8-b075-09a9fa0c64c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019ca039-12b7-7df3-abba-445e14051d04" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-75d2-ab56-8ec48885a52a" xlink:to="loc_country_MX_019ca039-12b7-7df3-abba-445e14051d04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_019ca039-12b7-7aed-8282-faaf8d580504" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-75d2-ab56-8ec48885a52a" xlink:to="loc_country_CA_019ca039-12b7-7aed-8282-faaf8d580504" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_OtherGeographicalLocationMember_019ca039-12b7-7679-95a0-51109c96cb35" xlink:href="cmt-20251231.xsd#cmt_OtherGeographicalLocationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-12b7-75d2-ab56-8ec48885a52a" xlink:to="loc_cmt_OtherGeographicalLocationMember_019ca039-12b7-7679-95a0-51109c96cb35" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-12b7-71b1-949a-5299162cdf2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019ca039-12b7-7f96-8e9f-ff954379ec3e" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-12b7-71b1-949a-5299162cdf2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019ca039-12b7-76e7-9acb-a6e6fd00a338" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019ca039-12b7-7f96-8e9f-ff954379ec3e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019ca039-12b7-76e7-9acb-a6e6fd00a338" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/PropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#PropertyPlantandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/PropertyPlantandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-746d-8e57-de6e4480341b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-746d-8e57-de6e4480341b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7c7f-a0bb-76208ddaa309" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-746d-8e57-de6e4480341b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7c7f-a0bb-76208ddaa309" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-7c7f-a0bb-76208ddaa309_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7c7f-a0bb-76208ddaa309" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-7c7f-a0bb-76208ddaa309_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ca039-12b7-7c7f-a0bb-76208ddaa309" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAndLandImprovementsMember_019ca039-12b7-7b06-b2d6-b1994b4a6531" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandAndLandImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:to="loc_us-gaap_LandAndLandImprovementsMember_019ca039-12b7-7b06-b2d6-b1994b4a6531" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingMember_019ca039-12b7-7a84-829e-c9e58ecc9d58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:to="loc_us-gaap_BuildingMember_019ca039-12b7-7a84-829e-c9e58ecc9d58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_019ca039-12b7-7263-9664-61dbb2e327b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_019ca039-12b7-7263-9664-61dbb2e327b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ToolsDiesAndMoldsMember_019ca039-12b7-7eaa-9b42-e18ab37e0612" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ToolsDiesAndMoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:to="loc_us-gaap_ToolsDiesAndMoldsMember_019ca039-12b7-7eaa-9b42-e18ab37e0612" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetUnderConstructionMember_019ca039-12b7-72b3-a27c-70ceeefe9b45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetUnderConstructionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ca039-12b7-73c6-9580-128d2a787131" xlink:to="loc_us-gaap_AssetUnderConstructionMember_019ca039-12b7-72b3-a27c-70ceeefe9b45" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019ca039-12b7-71d6-b8a2-3a94fdcb9d84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-746d-8e57-de6e4480341b" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019ca039-12b7-71d6-b8a2-3a94fdcb9d84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019ca039-12b7-71d6-b8a2-3a94fdcb9d84_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019ca039-12b7-71d6-b8a2-3a94fdcb9d84" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019ca039-12b7-71d6-b8a2-3a94fdcb9d84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019ca039-12b7-7357-9318-324fdff80e5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019ca039-12b7-71d6-b8a2-3a94fdcb9d84" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019ca039-12b7-7357-9318-324fdff80e5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_AccountsPayableCurrentMember_019ca039-12b7-7e42-91b1-87ed9599f368" xlink:href="cmt-20251231.xsd#cmt_AccountsPayableCurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-12b7-7357-9318-324fdff80e5c" xlink:to="loc_cmt_AccountsPayableCurrentMember_019ca039-12b7-7e42-91b1-87ed9599f368" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019cb99d-c67f-7a58-b3e8-c3addb482450" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ca039-12b7-746d-8e57-de6e4480341b" xlink:to="loc_srt_StatementGeographicalAxis_019cb99d-c67f-7a58-b3e8-c3addb482450" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019cb99d-c67f-7a58-b3e8-c3addb482450_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019cb99d-c67f-7a58-b3e8-c3addb482450" xlink:to="loc_srt_SegmentGeographicalDomain_019cb99d-c67f-7a58-b3e8-c3addb482450_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019cb99d-c67f-746a-beec-ac782975f7e1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019cb99d-c67f-7a58-b3e8-c3addb482450" xlink:to="loc_srt_SegmentGeographicalDomain_019cb99d-c67f-746a-beec-ac782975f7e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019cb99d-e539-7217-9e84-133c2a2ff361" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019cb99d-c67f-746a-beec-ac782975f7e1" xlink:to="loc_country_MX_019cb99d-e539-7217-9e84-133c2a2ff361" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019ca039-12b7-7c72-8d55-f80ad67a588e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019ca039-12b7-7c72-8d55-f80ad67a588e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019ca039-12b7-7bc1-9bf2-ce1f07dbf2df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019ca039-12b7-7bc1-9bf2-ce1f07dbf2df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019ca039-12b7-75c6-b468-a494a42cb6ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019ca039-12b7-75c6-b468-a494a42cb6ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_PropertyPlantAndEquipmentCommitments_019cbed2-20db-73f2-bfd9-055b883cb884" xlink:href="cmt-20251231.xsd#cmt_PropertyPlantAndEquipmentCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_cmt_PropertyPlantAndEquipmentCommitments_019cbed2-20db-73f2-bfd9-055b883cb884" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019ca039-12b7-7296-ba76-96a400ea26f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_AccountsPayableCurrent_019ca039-12b7-7296-ba76-96a400ea26f5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_019ca039-12b7-7d90-b227-38d9030dc53f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_Depreciation_019ca039-12b7-7d90-b227-38d9030dc53f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentDisposals_019cb99e-887a-7253-b887-d506dfd29fd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentDisposals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentDisposals_019cb99e-887a-7253-b887-d506dfd29fd1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationSaleOfPropertyPlantAndEquipment1_019cb99f-433a-7e09-855e-9680f5f57c95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationSaleOfPropertyPlantAndEquipment1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationSaleOfPropertyPlantAndEquipment1_019cb99f-433a-7e09-855e-9680f5f57c95" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019cb9a0-d8b8-7960-96b8-52f2ccccc1c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ca039-12b7-757a-8624-b3fa3daf9b4d" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019cb9a0-d8b8-7960-96b8-52f2ccccc1c8" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/LeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019ca039-12b7-714f-a02e-0c553a3c606b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019ca039-12b7-77e6-9833-2ec18577affd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019ca039-12b7-714f-a02e-0c553a3c606b" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019ca039-12b7-77e6-9833-2ec18577affd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ca039-12b7-7f57-bc3a-8879bbe91ab1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019ca039-12b7-77e6-9833-2ec18577affd" xlink:to="loc_srt_RangeAxis_019ca039-12b7-7f57-bc3a-8879bbe91ab1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7f57-bc3a-8879bbe91ab1_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7f57-bc3a-8879bbe91ab1" xlink:to="loc_srt_RangeMember_019ca039-12b7-7f57-bc3a-8879bbe91ab1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7c5c-9f40-f6f02414b0a0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7f57-bc3a-8879bbe91ab1" xlink:to="loc_srt_RangeMember_019ca039-12b7-7c5c-9f40-f6f02414b0a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ca039-12b7-7cd7-9ff4-17ca5fbee389" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7c5c-9f40-f6f02414b0a0" xlink:to="loc_srt_MinimumMember_019ca039-12b7-7cd7-9ff4-17ca5fbee389" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ca039-12b7-7d42-9f66-390553aef6cf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7c5c-9f40-f6f02414b0a0" xlink:to="loc_srt_MaximumMember_019ca039-12b7-7d42-9f66-390553aef6cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_019ca039-12b7-7bdb-8ae3-b022d84fabfd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019ca039-12b7-714f-a02e-0c553a3c606b" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_019ca039-12b7-7bdb-8ae3-b022d84fabfd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_LesseeOperatingLeaseWithOptionsToExtendLeaseTerm_019ca039-12b7-7780-bf9a-132dbab38f0a" xlink:href="cmt-20251231.xsd#cmt_LesseeOperatingLeaseWithOptionsToExtendLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019ca039-12b7-714f-a02e-0c553a3c606b" xlink:to="loc_cmt_LesseeOperatingLeaseWithOptionsToExtendLeaseTerm_019ca039-12b7-7780-bf9a-132dbab38f0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019ca039-12b7-753b-8ece-0a8f2e4c1e9d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019ca039-12b7-714f-a02e-0c553a3c606b" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019ca039-12b7-753b-8ece-0a8f2e4c1e9d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/LongTermIncentiveCompensationDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#LongTermIncentiveCompensationDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/LongTermIncentiveCompensationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb989-d89c-7bf2-a8a6-ae34a166f668" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb989-d89c-70c5-9808-20ed7450f7c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb989-d89c-7bf2-a8a6-ae34a166f668" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb989-d89c-70c5-9808-20ed7450f7c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019cb989-d89c-7cc4-84d5-5817d593cb5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb989-d89c-70c5-9808-20ed7450f7c4" xlink:to="loc_us-gaap_AwardTypeAxis_019cb989-d89c-7cc4-84d5-5817d593cb5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb989-d89c-7cc4-84d5-5817d593cb5d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019cb989-d89c-7cc4-84d5-5817d593cb5d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb989-d89c-7cc4-84d5-5817d593cb5d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb989-d89c-70f2-8f5e-1e48d81e766c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019cb989-d89c-7cc4-84d5-5817d593cb5d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb989-d89c-70f2-8f5e-1e48d81e766c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_019cb989-d89c-763c-b50f-ef218e7f9caf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb989-d89c-70f2-8f5e-1e48d81e766c" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_019cb989-d89c-763c-b50f-ef218e7f9caf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019cb98a-04d0-7b36-bf24-6a563b246261" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb989-d89c-7bf2-a8a6-ae34a166f668" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019cb98a-04d0-7b36-bf24-6a563b246261" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019cb989-f7ed-7133-903e-c304a7404b7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb989-d89c-7bf2-a8a6-ae34a166f668" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019cb989-f7ed-7133-903e-c304a7404b7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019cb989-d89c-7a0f-b7a1-044b4d887a4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb989-d89c-7bf2-a8a6-ae34a166f668" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019cb989-d89c-7a0f-b7a1-044b4d887a4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_019cbe9a-493e-78cb-b0a8-a01e0f7b14eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb989-d89c-7bf2-a8a6-ae34a166f668" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_019cbe9a-493e-78cb-b0a8-a01e0f7b14eb" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/GoodwillandIntangiblesScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#GoodwillandIntangiblesScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/GoodwillandIntangiblesScheduleofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019ca039-12b7-7bb3-95ed-ac2c3868386d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019ca039-12b7-7bb3-95ed-ac2c3868386d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ca039-12b7-7937-9ee3-17bf303cd86d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019ca039-12b7-7bb3-95ed-ac2c3868386d" xlink:to="loc_srt_RangeAxis_019ca039-12b7-7937-9ee3-17bf303cd86d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7937-9ee3-17bf303cd86d_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7937-9ee3-17bf303cd86d" xlink:to="loc_srt_RangeMember_019ca039-12b7-7937-9ee3-17bf303cd86d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7c59-95e5-4b5f00735295" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7937-9ee3-17bf303cd86d" xlink:to="loc_srt_RangeMember_019ca039-12b7-7c59-95e5-4b5f00735295" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ca039-12b7-7138-a786-ccf862688661" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7c59-95e5-4b5f00735295" xlink:to="loc_srt_MinimumMember_019ca039-12b7-7138-a786-ccf862688661" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ca039-12b7-702b-9509-4dfaabe2c221" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7c59-95e5-4b5f00735295" xlink:to="loc_srt_MaximumMember_019ca039-12b7-702b-9509-4dfaabe2c221" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-795f-9a00-3046d349e427" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019ca039-12b7-7bb3-95ed-ac2c3868386d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-795f-9a00-3046d349e427" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-795f-9a00-3046d349e427_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-795f-9a00-3046d349e427" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-795f-9a00-3046d349e427_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-715c-a449-3662d53521e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019ca039-12b7-795f-9a00-3046d349e427" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-715c-a449-3662d53521e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_019ca039-12b7-749f-bf36-f875f930cd4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-715c-a449-3662d53521e1" xlink:to="loc_us-gaap_TradeNamesMember_019ca039-12b7-749f-bf36-f875f930cd4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_019ca039-12b7-7ccb-a363-d5bdec3a34d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-715c-a449-3662d53521e1" xlink:to="loc_us-gaap_TrademarksMember_019ca039-12b7-7ccb-a363-d5bdec3a34d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_019ca039-12b7-7001-8b4b-0094c9bacc4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-715c-a449-3662d53521e1" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_019ca039-12b7-7001-8b4b-0094c9bacc4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_019ca039-12b7-7ed8-8a17-347683563095" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019ca039-12b7-715c-a449-3662d53521e1" xlink:to="loc_us-gaap_CustomerRelationshipsMember_019ca039-12b7-7ed8-8a17-347683563095" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019ca039-12b7-7756-b5c4-462173e43d2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019ca039-12b7-7756-b5c4-462173e43d2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019ca039-12b7-7de6-bde9-af736a95aa77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019ca039-12b7-7de6-bde9-af736a95aa77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019ca039-12b7-7df5-ac23-b4b94dd17dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019ca039-12b7-7df5-ac23-b4b94dd17dc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019ca039-12b7-72f6-a4be-3c6fa2566ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019ca039-12b7-72f6-a4be-3c6fa2566ce2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019ca039-12b7-7d7f-aec7-b5f412195d52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019ca039-12b7-7c62-bf03-6f57de75d788" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019ca039-12b7-7d7f-aec7-b5f412195d52" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/DebtScheduleLongtermDebtDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#DebtScheduleLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/DebtScheduleLongtermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7d08-98f3-4b45ee2d89d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-7985-99f4-878d97c9fa7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7d08-98f3-4b45ee2d89d1" xlink:to="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-7985-99f4-878d97c9fa7f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7ba3-b064-fdca4da4221f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-7985-99f4-878d97c9fa7f" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7ba3-b064-fdca4da4221f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7ba3-b064-fdca4da4221f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7ba3-b064-fdca4da4221f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7ba3-b064-fdca4da4221f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-78fe-b9e0-781f6c2bd640" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7ba3-b064-fdca4da4221f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-78fe-b9e0-781f6c2bd640" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayableMember_019ca039-12b7-7248-94e2-120f6440f747" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-78fe-b9e0-781f6c2bd640" xlink:to="loc_us-gaap_LoansPayableMember_019ca039-12b7-7248-94e2-120f6440f747" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019ca039-12b7-7f60-81ed-ce657a063e27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-78fe-b9e0-781f6c2bd640" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019ca039-12b7-7f60-81ed-ce657a063e27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7833-be67-78c9200dbea6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-7985-99f4-878d97c9fa7f" xlink:to="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7833-be67-78c9200dbea6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7833-be67-78c9200dbea6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7833-be67-78c9200dbea6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7833-be67-78c9200dbea6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7431-b10f-b4ff01769b85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7833-be67-78c9200dbea6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7431-b10f-b4ff01769b85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_FGITermLoansMember_019ca039-12b7-785f-b6cf-7b9e9883ab83" xlink:href="cmt-20251231.xsd#cmt_FGITermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7431-b10f-b4ff01769b85" xlink:to="loc_cmt_FGITermLoansMember_019ca039-12b7-785f-b6cf-7b9e9883ab83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_LeafCapitalTermLoansMember_019ca039-12b7-7fd7-9540-2d0366e66f97" xlink:href="cmt-20251231.xsd#cmt_LeafCapitalTermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7431-b10f-b4ff01769b85" xlink:to="loc_cmt_LeafCapitalTermLoansMember_019ca039-12b7-7fd7-9540-2d0366e66f97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_HuntingtonTermLoansMember_019ca039-12b7-7213-bb0e-21f8648f5301" xlink:href="cmt-20251231.xsd#cmt_HuntingtonTermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7431-b10f-b4ff01769b85" xlink:to="loc_cmt_HuntingtonTermLoansMember_019ca039-12b7-7213-bb0e-21f8648f5301" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019ca039-12b7-7f0b-8f11-ab0bd7b5ab63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7d08-98f3-4b45ee2d89d1" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019ca039-12b7-7f0b-8f11-ab0bd7b5ab63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_019ca039-12b7-7820-b2e1-2d07640e59ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7d08-98f3-4b45ee2d89d1" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_019ca039-12b7-7820-b2e1-2d07640e59ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019ca039-12b7-7571-9a9b-c236a4ffec02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7d08-98f3-4b45ee2d89d1" xlink:to="loc_us-gaap_LongTermDebtCurrent_019ca039-12b7-7571-9a9b-c236a4ffec02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ca039-12b7-7563-9b78-4650102d9e2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7d08-98f3-4b45ee2d89d1" xlink:to="loc_us-gaap_LongTermDebt_019ca039-12b7-7563-9b78-4650102d9e2f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/DebtNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7909-afaf-cbc672197195" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7909-afaf-cbc672197195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7909-afaf-cbc672197195_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7909-afaf-cbc672197195" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7909-afaf-cbc672197195_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7f05-8cfa-d1bef525ef0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ca039-12b7-7909-afaf-cbc672197195" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7f05-8cfa-d1bef525ef0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019ca039-12b7-737b-81bf-691e1d403126" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7f05-8cfa-d1bef525ef0a" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019ca039-12b7-737b-81bf-691e1d403126" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayableMember_019ca039-12b7-7b5b-a342-523e6bec73f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7f05-8cfa-d1bef525ef0a" xlink:to="loc_us-gaap_LoansPayableMember_019ca039-12b7-7b5b-a342-523e6bec73f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_SOFRLoansMember_019ca039-12b7-759b-ac64-10e822059690" xlink:href="cmt-20251231.xsd#cmt_SOFRLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7f05-8cfa-d1bef525ef0a" xlink:to="loc_cmt_SOFRLoansMember_019ca039-12b7-759b-ac64-10e822059690" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019ca039-12b7-749d-8ce0-0c1b9caa58d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ca039-12b7-7f05-8cfa-d1bef525ef0a" xlink:to="loc_us-gaap_SecuredDebtMember_019ca039-12b7-749d-8ce0-0c1b9caa58d4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019ca039-12b7-7e7a-b072-45b7e1ae1d1d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_us-gaap_VariableRateAxis_019ca039-12b7-7e7a-b072-45b7e1ae1d1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019ca039-12b7-7e7a-b072-45b7e1ae1d1d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019ca039-12b7-7e7a-b072-45b7e1ae1d1d" xlink:to="loc_us-gaap_VariableRateDomain_019ca039-12b7-7e7a-b072-45b7e1ae1d1d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019ca039-12b7-7d10-bb0d-d4b284c5c0fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019ca039-12b7-7e7a-b072-45b7e1ae1d1d" xlink:to="loc_us-gaap_VariableRateDomain_019ca039-12b7-7d10-bb0d-d4b284c5c0fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019ca039-12b7-7ec1-a7af-a64e4531b04f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalFundsEffectiveSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019ca039-12b7-7d10-bb0d-d4b284c5c0fe" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019ca039-12b7-7ec1-a7af-a64e4531b04f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_019ca039-12b7-761c-adfa-dc6fcea69cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019ca039-12b7-7d10-bb0d-d4b284c5c0fe" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_019ca039-12b7-761c-adfa-dc6fcea69cb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7f0f-b7d7-50caebf6e22b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7f0f-b7d7-50caebf6e22b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7f0f-b7d7-50caebf6e22b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7f0f-b7d7-50caebf6e22b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7f0f-b7d7-50caebf6e22b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ca039-12b7-7f0f-b7d7-50caebf6e22b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_HuntingtonTermLoansMember_019ca039-12b7-7539-91de-1ac389c1585d" xlink:href="cmt-20251231.xsd#cmt_HuntingtonTermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_HuntingtonTermLoansMember_019ca039-12b7-7539-91de-1ac389c1585d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_HuntingtonCapexLoanMember_019ca039-12b7-752f-aa88-1524d9fa62ee" xlink:href="cmt-20251231.xsd#cmt_HuntingtonCapexLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_HuntingtonCapexLoanMember_019ca039-12b7-752f-aa88-1524d9fa62ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_HuntingtonRevolvingLoanMember_019ca039-12b7-7cbe-95fd-b0cf0896e00b" xlink:href="cmt-20251231.xsd#cmt_HuntingtonRevolvingLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_HuntingtonRevolvingLoanMember_019ca039-12b7-7cbe-95fd-b0cf0896e00b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_LeafCapitalTermLoansMember_019ca039-12b7-7812-b00d-24714eab098f" xlink:href="cmt-20251231.xsd#cmt_LeafCapitalTermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_LeafCapitalTermLoansMember_019ca039-12b7-7812-b00d-24714eab098f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_FGITermLoansMember_019ca039-12b7-750f-99b5-cbceb2e55fe4" xlink:href="cmt-20251231.xsd#cmt_FGITermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_FGITermLoansMember_019ca039-12b7-750f-99b5-cbceb2e55fe4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_HuntingtonLoansMember_019ca039-12b7-7c9c-a583-ddb75296dcae" xlink:href="cmt-20251231.xsd#cmt_HuntingtonLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_HuntingtonLoansMember_019ca039-12b7-7c9c-a583-ddb75296dcae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_CreditAgreementMember_019ca039-12b7-7023-94e1-ef130297938d" xlink:href="cmt-20251231.xsd#cmt_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ca039-12b7-7b20-8419-08d437775893" xlink:to="loc_cmt_CreditAgreementMember_019ca039-12b7-7023-94e1-ef130297938d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019ca039-12b7-783d-b7e2-4d91517d5af2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_srt_CounterpartyNameAxis_019ca039-12b7-783d-b7e2-4d91517d5af2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019ca039-12b7-783d-b7e2-4d91517d5af2_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019ca039-12b7-783d-b7e2-4d91517d5af2" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019ca039-12b7-783d-b7e2-4d91517d5af2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019ca039-12b7-7c9a-9f9c-ef6eeb96c28b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019ca039-12b7-783d-b7e2-4d91517d5af2" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019ca039-12b7-7c9a-9f9c-ef6eeb96c28b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_HuntingtonLoansMember_019ca039-12b7-7bbb-92af-31a67467434b" xlink:href="cmt-20251231.xsd#cmt_HuntingtonLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019ca039-12b7-7c9a-9f9c-ef6eeb96c28b" xlink:to="loc_cmt_HuntingtonLoansMember_019ca039-12b7-7bbb-92af-31a67467434b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ca039-12b7-758c-955e-f0f64599f883" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_srt_RangeAxis_019ca039-12b7-758c-955e-f0f64599f883" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-758c-955e-f0f64599f883_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ca039-12b7-758c-955e-f0f64599f883" xlink:to="loc_srt_RangeMember_019ca039-12b7-758c-955e-f0f64599f883_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7c01-ba67-b30b27067f5b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ca039-12b7-758c-955e-f0f64599f883" xlink:to="loc_srt_RangeMember_019ca039-12b7-7c01-ba67-b30b27067f5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ca039-12b7-7d8e-9dd0-d1a261b828a8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7c01-ba67-b30b27067f5b" xlink:to="loc_srt_MinimumMember_019ca039-12b7-7d8e-9dd0-d1a261b828a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ca039-12b7-72f1-b7fb-3126041ac029" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7c01-ba67-b30b27067f5b" xlink:to="loc_srt_MaximumMember_019ca039-12b7-72f1-b7fb-3126041ac029" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-748b-bf2b-7ccb8282704b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-748b-bf2b-7ccb8282704b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-748b-bf2b-7ccb8282704b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-748b-bf2b-7ccb8282704b" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-748b-bf2b-7ccb8282704b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-713f-9265-d521ede127db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-12b7-748b-bf2b-7ccb8282704b" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-713f-9265-d521ede127db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019ca039-12b7-7470-b30d-ac08c343c9bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-12b7-713f-9265-d521ede127db" xlink:to="loc_us-gaap_InterestRateSwapMember_019ca039-12b7-7470-b30d-ac08c343c9bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019ca039-12b7-76cd-be45-f77392f922d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_us-gaap_HedgingDesignationAxis_019ca039-12b7-76cd-be45-f77392f922d5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019ca039-12b7-76cd-be45-f77392f922d5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019ca039-12b7-76cd-be45-f77392f922d5" xlink:to="loc_us-gaap_HedgingDesignationDomain_019ca039-12b7-76cd-be45-f77392f922d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019ca039-12b7-7bb3-9005-679fefd84dd2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019ca039-12b7-76cd-be45-f77392f922d5" xlink:to="loc_us-gaap_HedgingDesignationDomain_019ca039-12b7-7bb3-9005-679fefd84dd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019ca039-12b7-755e-85c1-e17c3acdb711" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019ca039-12b7-7bb3-9005-679fefd84dd2" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019ca039-12b7-755e-85c1-e17c3acdb711" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019ca039-12b7-7341-af88-4ea3a1eea3d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ca039-12b7-773f-bd7e-2467347c5758" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019ca039-12b7-7341-af88-4ea3a1eea3d4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-7341-af88-4ea3a1eea3d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019ca039-12b7-7341-af88-4ea3a1eea3d4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-7341-af88-4ea3a1eea3d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-704d-9a32-14281932542b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019ca039-12b7-7341-af88-4ea3a1eea3d4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-704d-9a32-14281932542b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019ca039-12b7-70b1-a503-e152f64de61a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-704d-9a32-14281932542b" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019ca039-12b7-70b1-a503-e152f64de61a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019ca039-12b7-7aa7-a621-65d8f3350f6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-704d-9a32-14281932542b" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019ca039-12b7-7aa7-a621-65d8f3350f6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_019ca039-12b7-74a6-8f5d-fc2353ff7f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019ca039-12b7-704d-9a32-14281932542b" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_019ca039-12b7-74a6-8f5d-fc2353ff7f9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019ca039-12b7-7e64-b108-9c9d65056942" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019ca039-12b7-7e64-b108-9c9d65056942" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019ca039-12b7-7970-ba9b-f2ec4e4e0c2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019ca039-12b7-7970-ba9b-f2ec4e4e0c2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019ca039-12b7-73f6-8df8-b7bff21e5044" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019ca039-12b7-73f6-8df8-b7bff21e5044" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditCurrent_019cbef8-14f3-7a74-bcba-ed231f8d5b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LinesOfCreditCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_LinesOfCreditCurrent_019cbef8-14f3-7a74-bcba-ed231f8d5b3a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_DebtInstrumentCovenantPercentageOfEquityInterests_019ca039-12b7-7597-92ee-495e534f74cb" xlink:href="cmt-20251231.xsd#cmt_DebtInstrumentCovenantPercentageOfEquityInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_cmt_DebtInstrumentCovenantPercentageOfEquityInterests_019ca039-12b7-7597-92ee-495e534f74cb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019ca039-12b7-71b3-b2a0-acb2f1a8ce7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019ca039-12b7-71b3-b2a0-acb2f1a8ce7e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanProcessingFee_019ca039-12b7-7dcf-a91d-d6728b40e00f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanProcessingFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_LoanProcessingFee_019ca039-12b7-7dcf-a91d-d6728b40e00f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019ca039-12b7-74b6-a0a1-a8f27314a6fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DebtInstrumentTerm_019ca039-12b7-74b6-a0a1-a8f27314a6fd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019ca039-12b7-7ed2-8d9e-546e70a481e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019ca039-12b7-7ed2-8d9e-546e70a481e0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_019ca039-12b7-73f6-9115-db0575e59704" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_019ca039-12b7-73f6-9115-db0575e59704" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ca039-12b7-769d-9951-022a021a87d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_LongTermDebt_019ca039-12b7-769d-9951-022a021a87d5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_019ca039-12b7-7ac4-b024-ac63d4a11e1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_019ca039-12b7-7ac4-b024-ac63d4a11e1e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_DebtInstrumentCommitments_019ca039-12b7-7d1f-b1ce-89cdaa18024c" xlink:href="cmt-20251231.xsd#cmt_DebtInstrumentCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_cmt_DebtInstrumentCommitments_019ca039-12b7-7d1f-b1ce-89cdaa18024c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPayment_019ca039-12b7-7aa5-b04d-28bc79e36072" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentPeriodicPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPayment_019ca039-12b7-7aa5-b04d-28bc79e36072" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019ca039-12b7-70d1-b50f-1af0787de0ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019ca039-12b7-70d1-b50f-1af0787de0ae" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_019ca039-12b7-73db-befa-5b4244faeb1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ca039-12b7-7084-b2ae-63cb419b8201" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_019ca039-12b7-73db-befa-5b4244faeb1f" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/StockBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#StockBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/StockBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-12b7-7271-bd2e-378fd3e52e98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-12b7-7271-bd2e-378fd3e52e98" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019ca039-12b7-763d-aa98-d1e8918dd25d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-12b7-7271-bd2e-378fd3e52e98" xlink:to="loc_us-gaap_PlanNameAxis_019ca039-12b7-763d-aa98-d1e8918dd25d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019ca039-12b7-763d-aa98-d1e8918dd25d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019ca039-12b7-763d-aa98-d1e8918dd25d" xlink:to="loc_us-gaap_PlanNameDomain_019ca039-12b7-763d-aa98-d1e8918dd25d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019ca039-12b7-7192-9e37-33132824136d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019ca039-12b7-763d-aa98-d1e8918dd25d" xlink:to="loc_us-gaap_PlanNameDomain_019ca039-12b7-7192-9e37-33132824136d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_A2021LongTermEquityIncentivePlanMember_019ca039-12b7-7176-b377-7997bb84eb2a" xlink:href="cmt-20251231.xsd#cmt_A2021LongTermEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019ca039-12b7-7192-9e37-33132824136d" xlink:to="loc_cmt_A2021LongTermEquityIncentivePlanMember_019ca039-12b7-7176-b377-7997bb84eb2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_A2006LongTermEquityIncentivePlanMember_019ca039-12b7-7fab-b22a-136c1071586b" xlink:href="cmt-20251231.xsd#cmt_A2006LongTermEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019ca039-12b7-7192-9e37-33132824136d" xlink:to="loc_cmt_A2006LongTermEquityIncentivePlanMember_019ca039-12b7-7fab-b22a-136c1071586b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019ca039-12b7-7f2e-ac89-b2eb54399a2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-12b7-7271-bd2e-378fd3e52e98" xlink:to="loc_us-gaap_AwardTypeAxis_019ca039-12b7-7f2e-ac89-b2eb54399a2c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7f2e-ac89-b2eb54399a2c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019ca039-12b7-7f2e-ac89-b2eb54399a2c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7f2e-ac89-b2eb54399a2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7546-9e72-0745d8b10b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019ca039-12b7-7f2e-ac89-b2eb54399a2c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7546-9e72-0745d8b10b3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019ca039-12b7-7d79-b242-79eb0a5d3717" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7546-9e72-0745d8b10b3a" xlink:to="loc_us-gaap_RestrictedStockMember_019ca039-12b7-7d79-b242-79eb0a5d3717" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember_019ca039-12b7-7f67-a74a-1bf5f8a1dd43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7546-9e72-0745d8b10b3a" xlink:to="loc_us-gaap_StockAppreciationRightsSARSMember_019ca039-12b7-7f67-a74a-1bf5f8a1dd43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019ca039-12b7-7a75-b0cb-a285126c3044" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-12b7-7546-9e72-0745d8b10b3a" xlink:to="loc_us-gaap_PerformanceSharesMember_019ca039-12b7-7a75-b0cb-a285126c3044" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019ca039-12b7-7909-bdbd-ec88a2f9d480" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-12b7-7271-bd2e-378fd3e52e98" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019ca039-12b7-7909-bdbd-ec88a2f9d480" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019ca039-12b7-7909-bdbd-ec88a2f9d480_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019ca039-12b7-7909-bdbd-ec88a2f9d480" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019ca039-12b7-7909-bdbd-ec88a2f9d480_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019ca039-12b7-754f-aa1a-8cec337676bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019ca039-12b7-7909-bdbd-ec88a2f9d480" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019ca039-12b7-754f-aa1a-8cec337676bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_019ca039-12b7-7eac-a911-df6f07c3e519" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019ca039-12b7-754f-aa1a-8cec337676bc" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_019ca039-12b7-7eac-a911-df6f07c3e519" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_019ca039-12b7-7d7e-8101-6a900fa7bc51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019ca039-12b7-754f-aa1a-8cec337676bc" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_019ca039-12b7-7d7e-8101-6a900fa7bc51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ca039-12b7-7c57-b39e-79c9cdd09c74" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-12b7-7271-bd2e-378fd3e52e98" xlink:to="loc_srt_RangeAxis_019ca039-12b7-7c57-b39e-79c9cdd09c74" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7c57-b39e-79c9cdd09c74_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7c57-b39e-79c9cdd09c74" xlink:to="loc_srt_RangeMember_019ca039-12b7-7c57-b39e-79c9cdd09c74_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-12b7-7d3c-8af9-69d3607c1f46" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ca039-12b7-7c57-b39e-79c9cdd09c74" xlink:to="loc_srt_RangeMember_019ca039-12b7-7d3c-8af9-69d3607c1f46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ca039-12b7-77d4-9dc4-921a4b002fae" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7d3c-8af9-69d3607c1f46" xlink:to="loc_srt_MinimumMember_019ca039-12b7-77d4-9dc4-921a4b002fae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ca039-12b7-76b5-bba6-9fe69984d9aa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-12b7-7d3c-8af9-69d3607c1f46" xlink:to="loc_srt_MaximumMember_019ca039-12b7-76b5-bba6-9fe69984d9aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019ca039-12b7-771e-9a9e-2ac4500379c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019ca039-12b7-771e-9a9e-2ac4500379c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019ca039-12b7-74a7-9346-2961df284645" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019ca039-12b7-74a7-9346-2961df284645" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ShareBasedCompensationArrangementByShareBasedPaymentAwardContractualTerm_019cb99a-9622-7d22-b111-2d6754761914" xlink:href="cmt-20251231.xsd#cmt_ShareBasedCompensationArrangementByShareBasedPaymentAwardContractualTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_cmt_ShareBasedCompensationArrangementByShareBasedPaymentAwardContractualTerm_019cb99a-9622-7d22-b111-2d6754761914" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019ca039-12b7-788e-8c18-6dc5f06f82fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019ca039-12b7-788e-8c18-6dc5f06f82fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_019ca039-12b7-7952-a819-08a48be4658a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_019ca039-12b7-7952-a819-08a48be4658a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019ca039-12b7-7a5f-9eb1-337e3f5f52df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019ca039-12b7-7a5f-9eb1-337e3f5f52df" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019ca039-136e-70c3-b7f7-7b34e97c17cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019ca039-136e-70c3-b7f7-7b34e97c17cf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019ca039-136e-7b80-aeb4-0303493e4da3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019ca039-136e-7b80-aeb4-0303493e4da3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ca039-136e-7f1f-af31-bea2d517d7f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ca039-136e-7f1f-af31-bea2d517d7f3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-78a3-a5c8-1d14ddb07f7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-78a3-a5c8-1d14ddb07f7b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019ca039-136e-74ab-b5d8-ad495643be01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019ca039-136e-74ab-b5d8-ad495643be01" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-7789-8827-37fc67fe2ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-7789-8827-37fc67fe2ef1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019ca039-136e-7789-93ca-8f56844209e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019ca039-136e-7789-93ca-8f56844209e6" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019ca039-136e-7844-8a7c-d8d8b3d97d64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019ca039-136e-7844-8a7c-d8d8b3d97d64" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsReclassifiedToLiabilityAwards_019cb991-3a58-7944-bfbe-7d5a57ac6d3a" xlink:href="cmt-20251231.xsd#cmt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsReclassifiedToLiabilityAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_cmt_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsReclassifiedToLiabilityAwards_019cb991-3a58-7944-bfbe-7d5a57ac6d3a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_APICShareBasedPaymentArrangementDecreaseForUnvestedEquityAwardsReclassifiedToLiabilityAccounting_019cb996-c10c-764d-935e-11d13dca5bdf" xlink:href="cmt-20251231.xsd#cmt_APICShareBasedPaymentArrangementDecreaseForUnvestedEquityAwardsReclassifiedToLiabilityAccounting"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_cmt_APICShareBasedPaymentArrangementDecreaseForUnvestedEquityAwardsReclassifiedToLiabilityAccounting_019cb996-c10c-764d-935e-11d13dca5bdf" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_019cbe94-abd0-7616-92f8-210ce8047438" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-12b7-7f7b-a41b-44607dc6ec2d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_019cbe94-abd0-7616-92f8-210ce8047438" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/StockBasedCompensationScheduleofRestrictedStockActivityDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#StockBasedCompensationScheduleofRestrictedStockActivityDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/StockBasedCompensationScheduleofRestrictedStockActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-756b-97f3-d3698853bf68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-136e-761b-8282-cf4de4635fb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-756b-97f3-d3698853bf68" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-136e-761b-8282-cf4de4635fb0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019ca039-136e-7fe6-b06c-fc2c895e4fd3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-136e-761b-8282-cf4de4635fb0" xlink:to="loc_us-gaap_AwardTypeAxis_019ca039-136e-7fe6-b06c-fc2c895e4fd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7fe6-b06c-fc2c895e4fd3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019ca039-136e-7fe6-b06c-fc2c895e4fd3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7fe6-b06c-fc2c895e4fd3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7415-945a-c3b64ca2f61a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019ca039-136e-7fe6-b06c-fc2c895e4fd3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7415-945a-c3b64ca2f61a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019ca039-136e-704b-82b3-ca038b6d2aad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7415-945a-c3b64ca2f61a" xlink:to="loc_us-gaap_RestrictedStockMember_019ca039-136e-704b-82b3-ca038b6d2aad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019ca039-136e-7191-a6d3-7cb981fc2b75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7415-945a-c3b64ca2f61a" xlink:to="loc_us-gaap_PerformanceSharesMember_019ca039-136e-7191-a6d3-7cb981fc2b75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ca039-136e-7eb6-b442-1173f54a1052" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-756b-97f3-d3698853bf68" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ca039-136e-7eb6-b442-1173f54a1052" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019ca039-136e-7249-a2bf-2f6de8b1a3bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ca039-136e-7eb6-b442-1173f54a1052" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019ca039-136e-7249-a2bf-2f6de8b1a3bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ca039-136e-7493-a0b0-c27a678fdc51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ca039-136e-7eb6-b442-1173f54a1052" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ca039-136e-7493-a0b0-c27a678fdc51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019ca039-136e-7b40-b14f-46b0f967eda8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ca039-136e-7eb6-b442-1173f54a1052" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019ca039-136e-7b40-b14f-46b0f967eda8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019ca039-136e-7fea-8a70-6ff6e067733a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ca039-136e-7eb6-b442-1173f54a1052" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019ca039-136e-7fea-8a70-6ff6e067733a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019ca039-136e-7d6b-9739-4c8a63bb0dc9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019ca039-136e-7b6e-b5a0-18da8ea5fea1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-756b-97f3-d3698853bf68" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019ca039-136e-7b6e-b5a0-18da8ea5fea1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019ca039-136e-70e5-ab66-4529f0ea5838" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019ca039-136e-7b6e-b5a0-18da8ea5fea1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019ca039-136e-70e5-ab66-4529f0ea5838" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-7c14-83ac-bfc7b29a24eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019ca039-136e-7b6e-b5a0-18da8ea5fea1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-7c14-83ac-bfc7b29a24eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-7e8d-8b67-75dbeeb0d0a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019ca039-136e-7b6e-b5a0-18da8ea5fea1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019ca039-136e-7e8d-8b67-75dbeeb0d0a2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019ca039-136e-7a4c-920d-b1fbe487b048" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019ca039-136e-7b6e-b5a0-18da8ea5fea1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019ca039-136e-7a4c-920d-b1fbe487b048" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019ca039-136e-7815-b324-4a903d940828" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/StockBasedCompensationScheduleofStockAppreciationRightsActivityDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#StockBasedCompensationScheduleofStockAppreciationRightsActivityDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/StockBasedCompensationScheduleofStockAppreciationRightsActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-7ec2-9769-12456100e614" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-136e-7493-bd35-6ab54dcd8b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-7ec2-9769-12456100e614" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-136e-7493-bd35-6ab54dcd8b3a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019ca039-136e-7d55-b45b-df0af172f52b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ca039-136e-7493-bd35-6ab54dcd8b3a" xlink:to="loc_us-gaap_AwardTypeAxis_019ca039-136e-7d55-b45b-df0af172f52b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7d55-b45b-df0af172f52b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019ca039-136e-7d55-b45b-df0af172f52b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-7d55-b45b-df0af172f52b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-76e9-82b8-77c4f8edee40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019ca039-136e-7d55-b45b-df0af172f52b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-76e9-82b8-77c4f8edee40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember_019ca039-136e-7b44-866e-808a641d78a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ca039-136e-76e9-82b8-77c4f8edee40" xlink:to="loc_us-gaap_StockAppreciationRightsSARSMember_019ca039-136e-7b44-866e-808a641d78a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward_019ca039-136e-7b37-9e3b-e42c85fb68e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-7ec2-9769-12456100e614" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward_019ca039-136e-7b37-9e3b-e42c85fb68e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_019ca039-136e-7023-b322-12c3f7456e5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward_019ca039-136e-7b37-9e3b-e42c85fb68e8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_019ca039-136e-7023-b322-12c3f7456e5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_019ca039-136e-7ffa-ba01-cb11bc4cc39c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward_019ca039-136e-7b37-9e3b-e42c85fb68e8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_019ca039-136e-7ffa-ba01-cb11bc4cc39c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019ca039-136e-718d-a949-f78b3040b74a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward_019ca039-136e-7b37-9e3b-e42c85fb68e8" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019ca039-136e-718d-a949-f78b3040b74a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_019ca039-136e-7a68-be6c-714ce57ddf29" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward_019ca039-136e-7b37-9e3b-e42c85fb68e8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_019ca039-136e-7a68-be6c-714ce57ddf29" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_019ca039-136e-75c8-bd59-8b2f6eeac03d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_019ca039-136e-73a4-85de-b37360e6166a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-7ec2-9769-12456100e614" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_019ca039-136e-73a4-85de-b37360e6166a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract_019ca039-136e-7843-b0ab-70015cbdbb24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-7ec2-9769-12456100e614" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract_019ca039-136e-7843-b0ab-70015cbdbb24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue_019ca039-136e-79a2-ad52-ecff338356ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract_019ca039-136e-7843-b0ab-70015cbdbb24" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue_019ca039-136e-79a2-ad52-ecff338356ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_019ca039-136e-7668-bc7e-0698d34bdb14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract_019ca039-136e-7843-b0ab-70015cbdbb24" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_019ca039-136e-7668-bc7e-0698d34bdb14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_019ca039-136e-7447-8c24-7b24a4ea1cb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract_019ca039-136e-7843-b0ab-70015cbdbb24" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_019ca039-136e-7447-8c24-7b24a4ea1cb5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue_019ca039-136e-7d2c-b0cc-f2d99e4d4dde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract_019ca039-136e-7843-b0ab-70015cbdbb24" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue_019ca039-136e-7d2c-b0cc-f2d99e4d4dde" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue_019ca039-136e-73d6-a56e-d3272b27aa9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_019ca039-136e-703c-867f-040ce6c31161" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ca039-136e-7ec2-9769-12456100e614" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_019ca039-136e-703c-867f-040ce6c31161" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/IncomeTaxesScheduleofProvisionforIncomeTaxesDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#IncomeTaxesScheduleofProvisionforIncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/IncomeTaxesScheduleofProvisionforIncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca08d-62eb-77a0-ba32-97dbfff8702d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019ca08d-62eb-7736-affe-615143b241d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca08d-62eb-77a0-ba32-97dbfff8702d" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019ca08d-62eb-7736-affe-615143b241d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_019ca08d-62eb-79c9-ad51-689dfe56fe7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019ca08d-62eb-7736-affe-615143b241d0" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_019ca08d-62eb-79c9-ad51-689dfe56fe7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019ca08d-62eb-79c9-ad51-689dfe56fe7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019ca08d-62eb-79c9-ad51-689dfe56fe7e" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019ca08d-62eb-79c9-ad51-689dfe56fe7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019ca08d-62eb-7b79-91b1-90252a2f5cbb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019ca08d-62eb-79c9-ad51-689dfe56fe7e" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019ca08d-62eb-7b79-91b1-90252a2f5cbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_019ca08d-e36b-7c20-b45d-9b8cd22d14d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StateAndLocalJurisdictionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019ca08d-62eb-7b79-91b1-90252a2f5cbb" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_019ca08d-e36b-7c20-b45d-9b8cd22d14d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxDisclosureAbstract_019ca039-136e-76dd-8ea7-8d0eda1efe75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca08d-62eb-77a0-ba32-97dbfff8702d" xlink:to="loc_us-gaap_IncomeTaxDisclosureAbstract_019ca039-136e-76dd-8ea7-8d0eda1efe75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-7dde-941a-fe3ef8b145d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxDisclosureAbstract_019ca039-136e-76dd-8ea7-8d0eda1efe75" xlink:to="loc_us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-7dde-941a-fe3ef8b145d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentFederalTaxExpenseBenefit_019ca039-136e-78ec-8e90-1324d8817ef8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentFederalTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-7dde-941a-fe3ef8b145d5" xlink:to="loc_us-gaap_CurrentFederalTaxExpenseBenefit_019ca039-136e-78ec-8e90-1324d8817ef8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentForeignTaxExpenseBenefit_019ca039-136e-7980-bc7c-2bba115b0910" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentForeignTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-7dde-941a-fe3ef8b145d5" xlink:to="loc_us-gaap_CurrentForeignTaxExpenseBenefit_019ca039-136e-7980-bc7c-2bba115b0910" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_019ca039-136e-7275-a581-45f6e54670e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-7dde-941a-fe3ef8b145d5" xlink:to="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_019ca039-136e-7275-a581-45f6e54670e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019ca039-136e-7943-9423-f1eccdee0b55" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-7dde-941a-fe3ef8b145d5" xlink:to="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_019ca039-136e-7943-9423-f1eccdee0b55" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-73fb-8edb-b278c4ffd03d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxDisclosureAbstract_019ca039-136e-76dd-8ea7-8d0eda1efe75" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-73fb-8edb-b278c4ffd03d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_019ca039-136e-7e0e-9022-0c078b54505f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFederalIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-73fb-8edb-b278c4ffd03d" xlink:to="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_019ca039-136e-7e0e-9022-0c078b54505f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_019ca039-136e-7a26-9b85-4923edb1a0be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredForeignIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-73fb-8edb-b278c4ffd03d" xlink:to="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_019ca039-136e-7a26-9b85-4923edb1a0be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_019ca039-136e-7881-ae8a-e4687c1da758" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-73fb-8edb-b278c4ffd03d" xlink:to="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_019ca039-136e-7881-ae8a-e4687c1da758" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019ca039-136e-732c-9e13-93207e9b4251" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefitContinuingOperationsAbstract_019ca039-136e-73fb-8edb-b278c4ffd03d" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_019ca039-136e-732c-9e13-93207e9b4251" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocationAbstract_019ca090-3ff6-7c28-97e3-ada865d2304b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxDisclosureAbstract_019ca039-136e-76dd-8ea7-8d0eda1efe75" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocationAbstract_019ca090-3ff6-7c28-97e3-ada865d2304b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_019ca08d-62eb-7ae8-b949-1eb11e579103" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocationAbstract_019ca090-3ff6-7c28-97e3-ada865d2304b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_019ca08d-62eb-7ae8-b949-1eb11e579103" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_019ca08f-3926-704b-aa55-b63273258abb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocationAbstract_019ca090-3ff6-7c28-97e3-ada865d2304b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_019ca08f-3926-704b-aa55-b63273258abb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019ca039-136e-7a38-a32f-3172967fe1a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocationAbstract_019ca090-3ff6-7c28-97e3-ada865d2304b" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019ca039-136e-7a38-a32f-3172967fe1a9" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/IncomeTaxesReconciliationofIncomeTaxProvisionDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#IncomeTaxesReconciliationofIncomeTaxProvisionDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/IncomeTaxesReconciliationofIncomeTaxProvisionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019ca09d-8fd1-7d9c-a8cc-bfa599959255" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019ca09d-8fd1-7d9c-a8cc-bfa599959255" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_019ca09d-8fd1-7e57-901b-c9e6bfda3dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019ca09d-8fd1-7d9c-a8cc-bfa599959255" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_019ca09d-8fd1-7e57-901b-c9e6bfda3dd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019ca09d-8fd1-7e57-901b-c9e6bfda3dd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019ca09d-8fd1-7e57-901b-c9e6bfda3dd4" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019ca09d-8fd1-7e57-901b-c9e6bfda3dd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019ca09d-8fd1-79ef-bff6-8c135c331979" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019ca09d-8fd1-7e57-901b-c9e6bfda3dd4" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019ca09d-8fd1-79ef-bff6-8c135c331979" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_019ca09e-0a83-7b64-9d7f-905a24dbfbe5" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019ca09d-8fd1-79ef-bff6-8c135c331979" xlink:to="loc_country_CA_019ca09e-0a83-7b64-9d7f-905a24dbfbe5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019ca09d-8fd1-70dc-b11a-f5bb0a09ade2" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019ca09d-8fd1-79ef-bff6-8c135c331979" xlink:to="loc_country_MX_019ca09d-8fd1-70dc-b11a-f5bb0a09ade2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_019ca039-136e-7891-a422-6362782a0532" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_019ca039-136e-7891-a422-6362782a0532" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_EffectiveIncomeTaxRateReconciliationStateAndLocalValuationAllowanceAmount_019ca039-136e-701a-91c0-1b444cb83f06" xlink:href="cmt-20251231.xsd#cmt_EffectiveIncomeTaxRateReconciliationStateAndLocalValuationAllowanceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_cmt_EffectiveIncomeTaxRateReconciliationStateAndLocalValuationAllowanceAmount_019ca039-136e-701a-91c0-1b444cb83f06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential_019ca039-136e-78b6-b763-74168c0e5abb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential_019ca039-136e-78b6-b763-74168c0e5abb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_019ca039-136e-7523-9227-add734253d1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_019ca039-136e-7523-9227-add734253d1e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustmentAmount_019caec5-1d65-7e62-b592-16c11fe8bc5b" xlink:href="cmt-20251231.xsd#cmt_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustmentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_cmt_EffectiveIncomeTaxRateReconciliationReturnToProvisionAdjustmentAmount_019caec5-1d65-7e62-b592-16c11fe8bc5b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther_019caecb-d208-7e24-bb15-bbd94d615e18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther_019caecb-d208-7e24-bb15-bbd94d615e18" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019ca039-136e-7df7-8ef9-e869a6b65161" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019ca039-136e-7df7-8ef9-e869a6b65161" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019cafe2-0bd4-757a-b878-d16ed0b5ed79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_019cafe2-0bd4-757a-b878-d16ed0b5ed79" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_019cafe2-0bd4-72e5-a8bf-bc5090a27d30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_019cafe2-0bd4-72e5-a8bf-bc5090a27d30" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationTaxCredits_019cafe2-0bd4-77fe-986f-8924a87167ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationTaxCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxReconciliationTaxCredits_019cafe2-0bd4-77fe-986f-8924a87167ad" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_019cafe2-0bd4-762c-925c-e07b2c811253" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_019cafe2-0bd4-762c-925c-e07b2c811253" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationFdiiAmount_019cafe2-0bd4-79a8-a3bb-b2d03f6f4110" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationFdiiAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationFdiiAmount_019cafe2-0bd4-79a8-a3bb-b2d03f6f4110" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationFdiiPercent_019cafe2-0bd4-7e56-aadb-cf6a119c407b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationFdiiPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationFdiiPercent_019cafe2-0bd4-7e56-aadb-cf6a119c407b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_EffectiveIncomeTaxRateReconciliationPermanentCompensationDifferencesAmount_019cafe2-0bd4-73c1-8dae-7aecbd96348c" xlink:href="cmt-20251231.xsd#cmt_EffectiveIncomeTaxRateReconciliationPermanentCompensationDifferencesAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_cmt_EffectiveIncomeTaxRateReconciliationPermanentCompensationDifferencesAmount_019cafe2-0bd4-73c1-8dae-7aecbd96348c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_EffectiveIncomeTaxRateReconciliationPermanentCompensationDifferencesPercent_019cafe2-0bd4-7987-b7f0-88345f45a1f3" xlink:href="cmt-20251231.xsd#cmt_EffectiveIncomeTaxRateReconciliationPermanentCompensationDifferencesPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_cmt_EffectiveIncomeTaxRateReconciliationPermanentCompensationDifferencesPercent_019cafe2-0bd4-7987-b7f0-88345f45a1f3" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther_019cafe2-0bd4-7d9c-9b89-b192f344b576" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOther_019cafe2-0bd4-7d9c-9b89-b192f344b576" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReconciliationOtherAdjustments_019cafe2-0bd4-7f6a-ae41-c44968b9c4d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxReconciliationOtherAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_IncomeTaxReconciliationOtherAdjustments_019cafe2-0bd4-7f6a-ae41-c44968b9c4d1" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_019cafe2-0bd4-7cbb-9425-08874296ee87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_019cafe2-0bd4-7cbb-9425-08874296ee87" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_019cafe2-0bd4-7cb1-b156-87603c56eb2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_019cafe2-0bd4-7cb1-b156-87603c56eb2b" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019cafe2-0bd4-700e-8299-a5304d05ce56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019ca09d-8fd1-7c53-8bd1-928a681e0778" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019cafe2-0bd4-700e-8299-a5304d05ce56" xlink:type="arc" order="19"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/IncomeTaxesNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#IncomeTaxesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowanceLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceTable_019ca039-136e-767d-a4ba-0d23b94fb635" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowanceTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_ValuationAllowanceTable_019ca039-136e-767d-a4ba-0d23b94fb635" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019ca039-136e-7773-93f2-5a57f80ad405" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ValuationAllowanceTable_019ca039-136e-767d-a4ba-0d23b94fb635" xlink:to="loc_srt_StatementGeographicalAxis_019ca039-136e-7773-93f2-5a57f80ad405" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-136e-7773-93f2-5a57f80ad405_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-136e-7773-93f2-5a57f80ad405" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-136e-7773-93f2-5a57f80ad405_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ca039-136e-7c31-848e-35ea6b3e0cd7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019ca039-136e-7773-93f2-5a57f80ad405" xlink:to="loc_srt_SegmentGeographicalDomain_019ca039-136e-7c31-848e-35ea6b3e0cd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_019ca039-136e-7372-8469-4ec54b8d06ba" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-136e-7c31-848e-35ea6b3e0cd7" xlink:to="loc_country_CA_019ca039-136e-7372-8469-4ec54b8d06ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019ca039-136e-714f-b176-340ce537a573" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ca039-136e-7c31-848e-35ea6b3e0cd7" xlink:to="loc_country_MX_019ca039-136e-714f-b176-340ce537a573" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_019ca039-136e-7d94-97d6-aa1f46fb4ac7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ValuationAllowanceTable_019ca039-136e-767d-a4ba-0d23b94fb635" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_019ca039-136e-7d94-97d6-aa1f46fb4ac7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019ca039-136e-7d94-97d6-aa1f46fb4ac7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019ca039-136e-7d94-97d6-aa1f46fb4ac7" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019ca039-136e-7d94-97d6-aa1f46fb4ac7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019ca039-136e-7fe0-b310-2166d9ad0231" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019ca039-136e-7d94-97d6-aa1f46fb4ac7" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019ca039-136e-7fe0-b310-2166d9ad0231" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_019ca039-136e-77bd-991b-ee296f4d86bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019ca039-136e-7fe0-b310-2166d9ad0231" xlink:to="loc_us-gaap_ForeignCountryMember_019ca039-136e-77bd-991b-ee296f4d86bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticCountryMember_019ca039-136e-7245-b1bc-a5a0b5ec87ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DomesticCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019ca039-136e-7fe0-b310-2166d9ad0231" xlink:to="loc_us-gaap_DomesticCountryMember_019ca039-136e-7245-b1bc-a5a0b5ec87ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsOfForeignSubsidiaries_019ca039-136e-7687-a0a8-6ada47e5bf75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UndistributedEarningsOfForeignSubsidiaries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_UndistributedEarningsOfForeignSubsidiaries_019ca039-136e-7687-a0a8-6ada47e5bf75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsNet_019ca039-136e-75e4-a5ae-31ed60d0039c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_DeferredTaxAssetsNet_019ca039-136e-75e4-a5ae-31ed60d0039c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilities_019ca039-136e-7943-8b45-8ebced5b85b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_DeferredTaxLiabilities_019ca039-136e-7943-8b45-8ebced5b85b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_019ca039-136e-7053-a13e-4ad47c9a1ba6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_019ca039-136e-7053-a13e-4ad47c9a1ba6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_019ca039-136e-7a52-8106-66b729503ba3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_OperatingLossCarryforwards_019ca039-136e-7a52-8106-66b729503ba3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_019ca039-136e-7cd7-aa55-5803185232f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_019ca039-136e-7cd7-aa55-5803185232f1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_019cbeb1-1303-7788-8a20-f0c75e533568" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceLineItems_019ca039-136e-757b-846b-deafc7fc37d1" xlink:to="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_019cbeb1-1303-7788-8a20-f0c75e533568" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/IncomeTaxesIncomeTaxesPaidDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#IncomeTaxesIncomeTaxesPaidDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/IncomeTaxesIncomeTaxesPaidDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019cafe7-2c7d-7a2c-905e-26242866900c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019cafe7-2c7d-7ee7-906d-ff5c9632401a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019cafe7-2c7d-7a2c-905e-26242866900c" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019cafe7-2c7d-7ee7-906d-ff5c9632401a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_019cafe7-2c7d-7e55-927f-0016c24b2960" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019cafe7-2c7d-7ee7-906d-ff5c9632401a" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_019cafe7-2c7d-7e55-927f-0016c24b2960" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019cafe7-2c7d-7e55-927f-0016c24b2960_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019cafe7-2c7d-7e55-927f-0016c24b2960" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019cafe7-2c7d-7e55-927f-0016c24b2960_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_019cafe7-2c7d-75fb-b09a-a20aa4a65a15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_019cafe7-2c7d-7e55-927f-0016c24b2960" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_019cafe7-2c7d-75fb-b09a-a20aa4a65a15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_019cafe7-2c7d-7f26-8ded-b7d39d606df2" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019cafe7-2c7d-75fb-b09a-a20aa4a65a15" xlink:to="loc_country_CA_019cafe7-2c7d-7f26-8ded-b7d39d606df2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_019cafe7-2c7d-7861-bfa8-b5394dc6fb42" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_019cafe7-2c7d-75fb-b09a-a20aa4a65a15" xlink:to="loc_country_MX_019cafe7-2c7d-7861-bfa8-b5394dc6fb42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidFederalAfterRefundReceived_019cafe7-2c7d-7d3a-97c0-22ee7c4481d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidFederalAfterRefundReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019cafe7-2c7d-7a2c-905e-26242866900c" xlink:to="loc_us-gaap_IncomeTaxPaidFederalAfterRefundReceived_019cafe7-2c7d-7d3a-97c0-22ee7c4481d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived_019cafe7-2c7d-7931-8160-00ee7e4630dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019cafe7-2c7d-7a2c-905e-26242866900c" xlink:to="loc_us-gaap_IncomeTaxPaidStateAndLocalAfterRefundReceived_019cafe7-2c7d-7931-8160-00ee7e4630dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPaidForeignAfterRefundReceived_019cafe7-2c7d-7db1-b3a9-5cdb9c16ac64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxPaidForeignAfterRefundReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019cafe7-2c7d-7a2c-905e-26242866900c" xlink:to="loc_us-gaap_IncomeTaxPaidForeignAfterRefundReceived_019cafe7-2c7d-7db1-b3a9-5cdb9c16ac64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_019cafe7-2c7d-7142-982b-73792adf7341" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019cafe7-2c7d-7a2c-905e-26242866900c" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_019cafe7-2c7d-7142-982b-73792adf7341" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/PostRetirementBenefitsNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#PostRetirementBenefitsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/PostRetirementBenefitsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-70c0-a91b-0c8b2608d21f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-70c0-a91b-0c8b2608d21f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019ca039-136e-7678-92a7-b27000df9b3e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-70c0-a91b-0c8b2608d21f" xlink:to="loc_srt_StatementScenarioAxis_019ca039-136e-7678-92a7-b27000df9b3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019ca039-136e-7678-92a7-b27000df9b3e_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019ca039-136e-7678-92a7-b27000df9b3e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019ca039-136e-7678-92a7-b27000df9b3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019ca039-136e-79ab-8b25-2f927ca7c21d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019ca039-136e-7678-92a7-b27000df9b3e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019ca039-136e-79ab-8b25-2f927ca7c21d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_019ca039-136e-7312-afd3-b5e060ac0f67" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019ca039-136e-79ab-8b25-2f927ca7c21d" xlink:to="loc_srt_ScenarioForecastMember_019ca039-136e-7312-afd3-b5e060ac0f67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7dff-8a41-8bd476d90efc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-70c0-a91b-0c8b2608d21f" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7dff-8a41-8bd476d90efc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7dff-8a41-8bd476d90efc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7dff-8a41-8bd476d90efc" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7dff-8a41-8bd476d90efc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7949-9d9e-66082327c467" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7dff-8a41-8bd476d90efc" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7949-9d9e-66082327c467" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019ca039-136e-722c-a5ae-c658e418bfa1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7949-9d9e-66082327c467" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019ca039-136e-722c-a5ae-c658e418bfa1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis_019ca039-136e-7c44-b7f7-ab365b92b95f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-70c0-a91b-0c8b2608d21f" xlink:to="loc_us-gaap_ValuationTechniqueAxis_019ca039-136e-7c44-b7f7-ab365b92b95f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019ca039-136e-7c44-b7f7-ab365b92b95f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019ca039-136e-7c44-b7f7-ab365b92b95f" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019ca039-136e-7c44-b7f7-ab365b92b95f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019ca039-136e-7677-96ea-7ffe9416eccc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019ca039-136e-7c44-b7f7-ab365b92b95f" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019ca039-136e-7677-96ea-7ffe9416eccc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_MedicalPostAge65Member_019ca039-136e-7417-a6a6-30fe46e5bf9d" xlink:href="cmt-20251231.xsd#cmt_MedicalPostAge65Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019ca039-136e-7677-96ea-7ffe9416eccc" xlink:to="loc_cmt_MedicalPostAge65Member_019ca039-136e-7417-a6a6-30fe46e5bf9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_DrugsMember_019ca039-136e-7918-84b7-74724f3d6554" xlink:href="cmt-20251231.xsd#cmt_DrugsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019ca039-136e-7677-96ea-7ffe9416eccc" xlink:to="loc_cmt_DrugsMember_019ca039-136e-7918-84b7-74724f3d6554" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedBenefitObligationIncreaseDecreaseForPlanAmendment_019ca039-136e-79a3-9c96-488a07467f71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAccumulatedBenefitObligationIncreaseDecreaseForPlanAmendment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedBenefitObligationIncreaseDecreaseForPlanAmendment_019ca039-136e-79a3-9c96-488a07467f71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_019ca039-136e-75df-a01d-a12c3938fd8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_019ca039-136e-75df-a01d-a12c3938fd8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_DefinedBenefitPlanNetPeriodicBenefitCostCreditImmediateRecognitionOfActuarialGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleListNotDisclosedFlag_019ca039-136e-79d6-9942-a23a44220c5b" xlink:href="cmt-20251231.xsd#cmt_DefinedBenefitPlanNetPeriodicBenefitCostCreditImmediateRecognitionOfActuarialGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleListNotDisclosedFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_cmt_DefinedBenefitPlanNetPeriodicBenefitCostCreditImmediateRecognitionOfActuarialGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleListNotDisclosedFlag_019ca039-136e-79d6-9942-a23a44220c5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_019ca039-136e-777b-97ca-d1c3836e56d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_019ca039-136e-777b-97ca-d1c3836e56d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_019ca039-136e-742b-b961-1fd7243e10ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_019ca039-136e-742b-b961-1fd7243e10ff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear_019ca039-136e-79b1-b3a9-4b3e4f49ea0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear_019ca039-136e-79b1-b3a9-4b3e4f49ea0b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear_019ca039-136e-7fcd-9ab3-a415d9e63fb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear_019ca039-136e-7fcd-9ab3-a415d9e63fb4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedAmortizationNextFiscalYear_019ca039-136e-734f-bead-97f56072afa9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedAmortizationNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedAmortizationNextFiscalYear_019ca039-136e-734f-bead-97f56072afa9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear_019ca039-136e-7867-b454-0288a4467675" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear_019ca039-136e-7867-b454-0288a4467675" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1_019ca039-136e-77a6-b289-e990e4501a07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-74d7-914f-1c3a938a94b4" xlink:to="loc_us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1_019ca039-136e-77a6-b289-e990e4501a07" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/PostRetirementBenefitsScheduleofinBenefitObligationDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#PostRetirementBenefitsScheduleofinBenefitObligationDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/PostRetirementBenefitsScheduleofinBenefitObligationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-71b5-9e7f-d406668a0acd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-791c-a71b-8a080e2343d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-71b5-9e7f-d406668a0acd" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-791c-a71b-8a080e2343d4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7a6b-9da0-2af4ec47ed3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-791c-a71b-8a080e2343d4" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7a6b-9da0-2af4ec47ed3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7a6b-9da0-2af4ec47ed3c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7a6b-9da0-2af4ec47ed3c" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7a6b-9da0-2af4ec47ed3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-73c8-a326-9cfd0ea7d1f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7a6b-9da0-2af4ec47ed3c" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-73c8-a326-9cfd0ea7d1f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019ca039-136e-7073-adfe-9c47b4c14140" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-73c8-a326-9cfd0ea7d1f1" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019ca039-136e-7073-adfe-9c47b4c14140" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_019ca039-136e-7081-9426-de9179c4c3b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-71b5-9e7f-d406668a0acd" xlink:to="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_019ca039-136e-7081-9426-de9179c4c3b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_019ca039-136e-734b-8508-eaefe4a7d260" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_019ca039-136e-7081-9426-de9179c4c3b8" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligation_019ca039-136e-734b-8508-eaefe4a7d260" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_019ca039-136e-7d6d-b4ed-2f0f0b5efa24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_019ca039-136e-7081-9426-de9179c4c3b8" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_019ca039-136e-7d6d-b4ed-2f0f0b5efa24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_019ca039-136e-7c1e-a479-cdddf840426f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_019ca039-136e-7081-9426-de9179c4c3b8" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_019ca039-136e-7c1e-a479-cdddf840426f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_019ca039-136e-7bd9-bfe1-5388f0f5bc8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward_019ca039-136e-7081-9426-de9179c4c3b8" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid_019ca039-136e-7bd9-bfe1-5388f0f5bc8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_019ca039-136e-78de-8465-79a1e9951230" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanBenefitObligation"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_019ca039-136e-797c-9b16-cd32487032c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-71b5-9e7f-d406668a0acd" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_019ca039-136e-797c-9b16-cd32487032c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_019ca039-136e-71d6-aedb-d2f39d559478" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-71b5-9e7f-d406668a0acd" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_019ca039-136e-71d6-aedb-d2f39d559478" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_019ca039-136e-7d17-8b34-9cacdaf9ebb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_019ca039-136e-71d6-aedb-d2f39d559478" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_019ca039-136e-7d17-8b34-9cacdaf9ebb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax_019ca039-136e-7d4e-8e13-d1fbf0a5d457" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_019ca039-136e-71d6-aedb-d2f39d559478" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax_019ca039-136e-7d4e-8e13-d1fbf0a5d457" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_019ca039-136e-7281-9471-ea2bd7b48c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract_019ca039-136e-71d6-aedb-d2f39d559478" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_019ca039-136e-7281-9471-ea2bd7b48c3b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_019ca039-136e-7716-a938-081ca36132a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-71b5-9e7f-d406668a0acd" xlink:to="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_019ca039-136e-7716-a938-081ca36132a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate_019ca039-136e-76f3-80a5-b641cae6abae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract_019ca039-136e-7716-a938-081ca36132a5" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate_019ca039-136e-76f3-80a5-b641cae6abae" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/PostRetirementBenefitsScheduleofFutureBenefitPaymentsDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#PostRetirementBenefitsScheduleofFutureBenefitPaymentsDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/PostRetirementBenefitsScheduleofFutureBenefitPaymentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-7901-a758-1fe5a5676481" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-7901-a758-1fe5a5676481" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7482-bcda-2fae29cfb542" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019ca039-136e-7901-a758-1fe5a5676481" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7482-bcda-2fae29cfb542" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7482-bcda-2fae29cfb542_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7482-bcda-2fae29cfb542" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7482-bcda-2fae29cfb542_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7bee-9094-ae66fe6cd559" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019ca039-136e-7482-bcda-2fae29cfb542" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7bee-9094-ae66fe6cd559" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019ca039-136e-71a6-8b3f-dae7f795da63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019ca039-136e-7bee-9094-ae66fe6cd559" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019ca039-136e-71a6-8b3f-dae7f795da63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths_019ca039-136e-76bb-90f8-50fac583683f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths_019ca039-136e-76bb-90f8-50fac583683f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo_019ca039-136e-7a21-b1b6-470c0945c8c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo_019ca039-136e-7a21-b1b6-470c0945c8c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree_019ca039-136e-704d-bb23-b6f13ff876ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree_019ca039-136e-704d-bb23-b6f13ff876ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour_019ca039-136e-7886-823c-43c8f6d80753" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour_019ca039-136e-7886-823c-43c8f6d80753" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive_019ca039-136e-7ad5-9c22-ffa326f83c78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive_019ca039-136e-7ad5-9c22-ffa326f83c78" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter_019ca039-136e-705a-a176-ccc01b25811b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019ca039-136e-7bfa-96bc-3abb84f1566c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter_019ca039-136e-705a-a176-ccc01b25811b" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/FairValueofFinancialInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#FairValueofFinancialInstrumentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/FairValueofFinancialInstrumentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7f88-a44d-100bb7491ee9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7f88-a44d-100bb7491ee9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7f88-a44d-100bb7491ee9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7f88-a44d-100bb7491ee9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7f88-a44d-100bb7491ee9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7f70-bb73-ff3c96172064" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7f88-a44d-100bb7491ee9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7f70-bb73-ff3c96172064" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019ca039-136e-7613-9f29-2e044dde6488" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7f70-bb73-ff3c96172064" xlink:to="loc_us-gaap_InterestRateSwapMember_019ca039-136e-7613-9f29-2e044dde6488" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019ca039-136e-71cf-bf63-af57a6710777" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7f70-bb73-ff3c96172064" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019ca039-136e-71cf-bf63-af57a6710777" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ca039-136e-7b98-8091-843ccb6582a1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:to="loc_srt_RangeAxis_019ca039-136e-7b98-8091-843ccb6582a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-136e-7b98-8091-843ccb6582a1_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ca039-136e-7b98-8091-843ccb6582a1" xlink:to="loc_srt_RangeMember_019ca039-136e-7b98-8091-843ccb6582a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ca039-136e-7331-a446-46a07c5f5c2d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ca039-136e-7b98-8091-843ccb6582a1" xlink:to="loc_srt_RangeMember_019ca039-136e-7331-a446-46a07c5f5c2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ca039-136e-7eab-8141-9490d7a2facf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-136e-7331-a446-46a07c5f5c2d" xlink:to="loc_srt_MaximumMember_019ca039-136e-7eab-8141-9490d7a2facf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ca039-136e-786f-8d6c-ed059d20b09d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ca039-136e-7331-a446-46a07c5f5c2d" xlink:to="loc_srt_MinimumMember_019ca039-136e-786f-8d6c-ed059d20b09d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_019ca039-136e-7c9f-a53c-3606e6c79f10" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:to="loc_srt_CurrencyAxis_019ca039-136e-7c9f-a53c-3606e6c79f10" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_019ca039-136e-7c9f-a53c-3606e6c79f10_default" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_019ca039-136e-7c9f-a53c-3606e6c79f10" xlink:to="loc_currency_AllCurrenciesDomain_019ca039-136e-7c9f-a53c-3606e6c79f10_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_019ca039-136e-7aee-b43a-415f90ce14bb" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_019ca039-136e-7c9f-a53c-3606e6c79f10" xlink:to="loc_currency_AllCurrenciesDomain_019ca039-136e-7aee-b43a-415f90ce14bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_MXN_019ca039-136e-778b-bad1-907b97c61ca5" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_MXN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_019ca039-136e-7aee-b43a-415f90ce14bb" xlink:to="loc_currency_MXN_019ca039-136e-778b-bad1-907b97c61ca5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_CAD_019ca039-136e-7bc1-8f5d-e5d380f94751" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_CAD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_019ca039-136e-7aee-b43a-415f90ce14bb" xlink:to="loc_currency_CAD_019ca039-136e-7bc1-8f5d-e5d380f94751" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-7cec-987d-2a094498f65c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:to="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-7cec-987d-2a094498f65c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-7cec-987d-2a094498f65c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-7cec-987d-2a094498f65c" xlink:to="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-7cec-987d-2a094498f65c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-74fa-9560-03a4b67f0d95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-7cec-987d-2a094498f65c" xlink:to="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-74fa-9560-03a4b67f0d95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019ca039-136e-7510-bf05-04de01b4e400" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-74fa-9560-03a4b67f0d95" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019ca039-136e-7510-bf05-04de01b4e400" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-7a66-9280-b1aa1deac87b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-79d6-89d0-de9969ccbbd4" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-7a66-9280-b1aa1deac87b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7a66-9280-b1aa1deac87b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-7a66-9280-b1aa1deac87b" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7a66-9280-b1aa1deac87b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-71c3-82fa-08e12d3e8dbd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-7a66-9280-b1aa1deac87b" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-71c3-82fa-08e12d3e8dbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_019ca039-136e-77b4-99f5-0fd47c16a34a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-71c3-82fa-08e12d3e8dbd" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_019ca039-136e-77b4-99f5-0fd47c16a34a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentAssetsMember_019ca039-136e-70aa-b9d2-beaf96300044" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-71c3-82fa-08e12d3e8dbd" xlink:to="loc_us-gaap_OtherNoncurrentAssetsMember_019ca039-136e-70aa-b9d2-beaf96300044" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_OtherAccruedLiabilitiesMember_019ca039-136e-7f47-99bf-a7495df72b0d" xlink:href="cmt-20251231.xsd#cmt_OtherAccruedLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-71c3-82fa-08e12d3e8dbd" xlink:to="loc_cmt_OtherAccruedLiabilitiesMember_019ca039-136e-7f47-99bf-a7495df72b0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_019ca039-136e-7c33-95fe-03b8c84a8b05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-71c3-82fa-08e12d3e8dbd" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_019ca039-136e-7c33-95fe-03b8c84a8b05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019ca039-136e-719d-bbea-8d19dbd5df32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019ca039-136e-719d-bbea-8d19dbd5df32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyExchangeRateTranslation1_019ca039-136e-71f0-9180-f8fca94c4a83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyExchangeRateTranslation1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:to="loc_us-gaap_ForeignCurrencyExchangeRateTranslation1_019ca039-136e-71f0-9180-f8fca94c4a83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_019ca039-136e-795e-8f3c-c9a7223bb9cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_019ca039-136e-795e-8f3c-c9a7223bb9cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019ca039-136e-7bbc-8081-8b076faf14b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019ca039-136e-7bbc-8081-8b076faf14b4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019ca039-136e-7fb8-8358-1db7b05d1e38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-71d5-88fe-4c6576b73e26" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019ca039-136e-7fb8-8358-1db7b05d1e38" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/FairValueofFinancialInstrumentsScheduleofDerivativesDesignatedasHedgingInstrumentsDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#FairValueofFinancialInstrumentsScheduleofDerivativesDesignatedasHedgingInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/FairValueofFinancialInstrumentsScheduleofDerivativesDesignatedasHedgingInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7c44-a303-196e321a8e2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-7000-97a0-d68cca960207" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7c44-a303-196e321a8e2d" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-7000-97a0-d68cca960207" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-745e-b5e7-ab8208599e0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-7000-97a0-d68cca960207" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-745e-b5e7-ab8208599e0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-745e-b5e7-ab8208599e0d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-745e-b5e7-ab8208599e0d" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-745e-b5e7-ab8208599e0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-782b-85d7-d3f245ad9824" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-745e-b5e7-ab8208599e0d" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-782b-85d7-d3f245ad9824" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019ca039-136e-7df9-8781-3e09bc640ed4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-782b-85d7-d3f245ad9824" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019ca039-136e-7df9-8781-3e09bc640ed4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019ca039-136e-734b-84ce-adcabdcd384c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-782b-85d7-d3f245ad9824" xlink:to="loc_us-gaap_InterestRateSwapMember_019ca039-136e-734b-84ce-adcabdcd384c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-76d4-8a47-8f1fa105abfb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-7000-97a0-d68cca960207" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-76d4-8a47-8f1fa105abfb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-76d4-8a47-8f1fa105abfb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-76d4-8a47-8f1fa105abfb" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-76d4-8a47-8f1fa105abfb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7c15-9003-1a9b87da6af9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019ca039-136e-76d4-8a47-8f1fa105abfb" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7c15-9003-1a9b87da6af9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_019ca039-136e-73dc-9d0f-1333dc216f3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7c15-9003-1a9b87da6af9" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_019ca039-136e-73dc-9d0f-1333dc216f3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentAssetsMember_019ca039-136e-7602-85ec-f3578145b107" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7c15-9003-1a9b87da6af9" xlink:to="loc_us-gaap_OtherNoncurrentAssetsMember_019ca039-136e-7602-85ec-f3578145b107" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_OtherAccruedLiabilitiesMember_019ca039-136e-7da2-b3b8-f68b8ed39aa9" xlink:href="cmt-20251231.xsd#cmt_OtherAccruedLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7c15-9003-1a9b87da6af9" xlink:to="loc_cmt_OtherAccruedLiabilitiesMember_019ca039-136e-7da2-b3b8-f68b8ed39aa9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_019ca039-136e-7a0f-b9d8-f706b34ee9e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019ca039-136e-7c15-9003-1a9b87da6af9" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_019ca039-136e-7a0f-b9d8-f706b34ee9e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-77d0-a6a5-6e11efe1ccc6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-7000-97a0-d68cca960207" xlink:to="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-77d0-a6a5-6e11efe1ccc6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-77d0-a6a5-6e11efe1ccc6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-77d0-a6a5-6e11efe1ccc6" xlink:to="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-77d0-a6a5-6e11efe1ccc6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-7c39-993c-0255c000b766" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019ca039-136e-77d0-a6a5-6e11efe1ccc6" xlink:to="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-7c39-993c-0255c000b766" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019ca039-136e-7db4-822e-8b4fff2376ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019ca039-136e-7c39-993c-0255c000b766" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019ca039-136e-7db4-822e-8b4fff2376ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019ca039-136e-76c0-b3e5-9846d6336be7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7c44-a303-196e321a8e2d" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019ca039-136e-76c0-b3e5-9846d6336be7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019ca039-136e-796d-8cc7-2bbdc35ceb4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7c44-a303-196e321a8e2d" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019ca039-136e-796d-8cc7-2bbdc35ceb4f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/FairValueofFinancialInstrumentsScheduleofUnrealizedandRealizedGainandLossRecognizedinAOCIDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#FairValueofFinancialInstrumentsScheduleofUnrealizedandRealizedGainandLossRecognizedinAOCIDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/FairValueofFinancialInstrumentsScheduleofUnrealizedandRealizedGainandLossRecognizedinAOCIDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7e3a-a0cc-d61f45748d46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-768b-af8a-53a2dd63ba53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7e3a-a0cc-d61f45748d46" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-768b-af8a-53a2dd63ba53" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7fda-b371-e8ab25c6ea23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-768b-af8a-53a2dd63ba53" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7fda-b371-e8ab25c6ea23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7fda-b371-e8ab25c6ea23_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7fda-b371-e8ab25c6ea23" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7fda-b371-e8ab25c6ea23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7a87-b903-9ed94576a80f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019ca039-136e-7fda-b371-e8ab25c6ea23" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7a87-b903-9ed94576a80f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019ca039-136e-7155-bf0d-9f2cf22e6ed3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7a87-b903-9ed94576a80f" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019ca039-136e-7155-bf0d-9f2cf22e6ed3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019ca039-136e-7400-8f89-ab1651ccd553" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019ca039-136e-7a87-b903-9ed94576a80f" xlink:to="loc_us-gaap_InterestRateSwapMember_019ca039-136e-7400-8f89-ab1651ccd553" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019ca039-136e-7f86-8366-4f51f6ee337d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019ca039-136e-768b-af8a-53a2dd63ba53" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019ca039-136e-7f86-8366-4f51f6ee337d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7f86-8366-4f51f6ee337d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019ca039-136e-7f86-8366-4f51f6ee337d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7f86-8366-4f51f6ee337d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7667-a5e7-5ca0b93c93f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019ca039-136e-7f86-8366-4f51f6ee337d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7667-a5e7-5ca0b93c93f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_019ca039-136e-7adb-8906-2823b3d6fe07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7667-a5e7-5ca0b93c93f5" xlink:to="loc_us-gaap_CostOfSalesMember_019ca039-136e-7adb-8906-2823b3d6fe07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_019ca039-136e-78ac-850c-6b30b5ba0c04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7667-a5e7-5ca0b93c93f5" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_019ca039-136e-78ac-850c-6b30b5ba0c04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseMember_019ca039-136e-7798-b9b9-2d2e4a267a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019ca039-136e-7667-a5e7-5ca0b93c93f5" xlink:to="loc_us-gaap_InterestExpenseMember_019ca039-136e-7798-b9b9-2d2e4a267a5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_019ca039-136e-7d22-a995-73663e7e9f06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7e3a-a0cc-d61f45748d46" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_019ca039-136e-7d22-a995-73663e7e9f06" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_019ca039-136e-711c-bb37-23b11074a849" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019ca039-136e-7e3a-a0cc-d61f45748d46" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_019ca039-136e-711c-bb37-23b11074a849" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/AccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#AccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/AccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019ca039-136e-7046-a8b9-a425bff528b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019ca039-136e-7277-9b40-09cbb2947787" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019ca039-136e-7046-a8b9-a425bff528b7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019ca039-136e-7277-9b40-09cbb2947787" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019ca039-136e-79aa-a129-1b5c71de6091" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019ca039-136e-7277-9b40-09cbb2947787" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019ca039-136e-79aa-a129-1b5c71de6091" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ca039-136e-79aa-a129-1b5c71de6091_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ca039-136e-79aa-a129-1b5c71de6091" xlink:to="loc_us-gaap_EquityComponentDomain_019ca039-136e-79aa-a129-1b5c71de6091_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ca039-136e-7ea3-a2aa-1e49c61862fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ca039-136e-79aa-a129-1b5c71de6091" xlink:to="loc_us-gaap_EquityComponentDomain_019ca039-136e-7ea3-a2aa-1e49c61862fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019ca039-136e-74a7-8a87-9475a9bbff71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-136e-7ea3-a2aa-1e49c61862fa" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019ca039-136e-74a7-8a87-9475a9bbff71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019ca039-136e-78ee-9129-c60732a5e2d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-136e-7ea3-a2aa-1e49c61862fa" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019ca039-136e-78ee-9129-c60732a5e2d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019ca039-136e-76dd-880f-5d362b703d72" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ca039-136e-7ea3-a2aa-1e49c61862fa" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019ca039-136e-76dd-880f-5d362b703d72" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019ca039-136e-7995-9294-9ba9bc3499ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019ca039-136e-7046-a8b9-a425bff528b7" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019ca039-136e-7995-9294-9ba9bc3499ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ca039-136e-72af-9ef1-84208faef36e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019ca039-136e-7995-9294-9ba9bc3499ae" xlink:to="loc_us-gaap_StockholdersEquity_019ca039-136e-72af-9ef1-84208faef36e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019ca039-136e-713c-8387-83c127b2e3ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019ca039-136e-7995-9294-9ba9bc3499ae" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019ca039-136e-713c-8387-83c127b2e3ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019ca039-136e-7c84-9758-fee101de1821" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019ca039-136e-7995-9294-9ba9bc3499ae" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019ca039-136e-7c84-9758-fee101de1821" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_019ca039-136e-7b9d-8a68-684460dccff4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019ca039-136e-7995-9294-9ba9bc3499ae" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_019ca039-136e-7b9d-8a68-684460dccff4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ca039-136e-7e97-a2ae-ed8a992110df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/SegmentReportingDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#SegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/SegmentReportingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ca039-136e-749c-93ba-777d9b1bd805" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ca039-136e-749c-93ba-777d9b1bd805" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019ca039-136e-74a6-a2bc-3269790c3330" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ca039-136e-749c-93ba-777d9b1bd805" xlink:to="loc_srt_ProductOrServiceAxis_019ca039-136e-74a6-a2bc-3269790c3330" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ca039-136e-74a6-a2bc-3269790c3330_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019ca039-136e-74a6-a2bc-3269790c3330" xlink:to="loc_srt_ProductsAndServicesDomain_019ca039-136e-74a6-a2bc-3269790c3330_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ca039-136e-7350-8057-18868f9a2d47" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019ca039-136e-74a6-a2bc-3269790c3330" xlink:to="loc_srt_ProductsAndServicesDomain_019ca039-136e-7350-8057-18868f9a2d47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_019ca039-136e-7cb2-af73-48dc0cf98904" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ca039-136e-7350-8057-18868f9a2d47" xlink:to="loc_us-gaap_ProductMember_019ca039-136e-7cb2-af73-48dc0cf98904" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019ca039-136e-7e7b-9002-33c57e8c6567" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ca039-136e-7350-8057-18868f9a2d47" xlink:to="loc_us-gaap_ServiceMember_019ca039-136e-7e7b-9002-33c57e8c6567" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019ca039-136e-7517-b5eb-f494ef2acbed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ca039-136e-749c-93ba-777d9b1bd805" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019ca039-136e-7517-b5eb-f494ef2acbed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019ca039-136e-7517-b5eb-f494ef2acbed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019ca039-136e-7517-b5eb-f494ef2acbed" xlink:to="loc_us-gaap_SegmentDomain_019ca039-136e-7517-b5eb-f494ef2acbed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019ca039-136e-7f49-a5a5-54ce7bd20b66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019ca039-136e-7517-b5eb-f494ef2acbed" xlink:to="loc_us-gaap_SegmentDomain_019ca039-136e-7f49-a5a5-54ce7bd20b66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_ReportableSegmentMember_019ca039-136e-7627-bd50-c8d6fb40749d" xlink:href="cmt-20251231.xsd#cmt_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019ca039-136e-7f49-a5a5-54ce7bd20b66" xlink:to="loc_cmt_ReportableSegmentMember_019ca039-136e-7627-bd50-c8d6fb40749d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-136e-77ca-9a96-8ff4afe1b930" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-136e-77ca-9a96-8ff4afe1b930" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_VariableCostOfRevenue_019ca039-136e-7dce-a65a-84052b2a4fc0" xlink:href="cmt-20251231.xsd#cmt_VariableCostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_cmt_VariableCostOfRevenue_019ca039-136e-7dce-a65a-84052b2a4fc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_FixedCostOfRevenue_019ca039-136e-7058-8dbd-908b6865c855" xlink:href="cmt-20251231.xsd#cmt_FixedCostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_cmt_FixedCostOfRevenue_019ca039-136e-7058-8dbd-908b6865c855" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019ca039-136e-7817-b795-5b402b654469" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019ca039-136e-7817-b795-5b402b654469" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019ca039-136e-7489-a499-b083f89be004" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_OperatingIncomeLoss_019ca039-136e-7489-a499-b083f89be004" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019ca039-136e-7258-9fc3-a5b6c812c78c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019ca039-136e-7258-9fc3-a5b6c812c78c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019ca039-136e-763c-80cc-924a4e6a6a22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_InterestExpense_019ca039-136e-763c-80cc-924a4e6a6a22" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019ca039-136e-787e-963b-0e70d316b99a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019ca039-136e-787e-963b-0e70d316b99a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ca039-136e-7813-b3aa-0e7f7206c0f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ca039-136e-7b68-a1c8-846feb816df2" xlink:to="loc_us-gaap_NetIncomeLoss_019ca039-136e-7813-b3aa-0e7f7206c0f3" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/QuarterlyResultsofOperationsUnauditedDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#QuarterlyResultsofOperationsUnauditedDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/QuarterlyResultsofOperationsUnauditedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019ca039-136e-7db0-a4cf-1f9bcae5f6be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019ca039-136e-7b54-8e11-ec4b08a65162" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019ca039-136e-7db0-a4cf-1f9bcae5f6be" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019ca039-136e-7b54-8e11-ec4b08a65162" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019ca039-136e-73dc-bb6f-ebde6274a615" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019ca039-136e-7b54-8e11-ec4b08a65162" xlink:to="loc_srt_ProductOrServiceAxis_019ca039-136e-73dc-bb6f-ebde6274a615" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ca039-136e-73dc-bb6f-ebde6274a615_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019ca039-136e-73dc-bb6f-ebde6274a615" xlink:to="loc_srt_ProductsAndServicesDomain_019ca039-136e-73dc-bb6f-ebde6274a615_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ca039-136e-7c06-b7e3-df3953dea4a4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019ca039-136e-73dc-bb6f-ebde6274a615" xlink:to="loc_srt_ProductsAndServicesDomain_019ca039-136e-7c06-b7e3-df3953dea4a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_019ca039-136e-70b6-b999-0af81571c189" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ca039-136e-7c06-b7e3-df3953dea4a4" xlink:to="loc_us-gaap_ProductMember_019ca039-136e-70b6-b999-0af81571c189" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_019ca039-136e-7c3b-ab4f-e2f292134433" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ca039-136e-7c06-b7e3-df3953dea4a4" xlink:to="loc_us-gaap_ServiceMember_019ca039-136e-7c3b-ab4f-e2f292134433" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SelectedQuarterlyFinancialInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019ca039-136e-7db0-a4cf-1f9bcae5f6be" xlink:to="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-136e-74de-b1f3-bb663580ad11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ca039-136e-74de-b1f3-bb663580ad11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019ca039-136e-7b32-a23e-9784736d9c2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:to="loc_us-gaap_GrossProfit_019ca039-136e-7b32-a23e-9784736d9c2e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019ca039-136e-7fbe-a852-57eafdbcbb94" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:to="loc_us-gaap_OperatingIncomeLoss_019ca039-136e-7fbe-a852-57eafdbcbb94" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ca039-136e-76e8-9de6-1927ab36eb32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:to="loc_us-gaap_NetIncomeLoss_019ca039-136e-76e8-9de6-1927ab36eb32" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_019ca039-136e-728c-9fa7-486c75f6f949" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SelectedQuarterlyFinancialInformationAbstract_019ca039-136e-7762-9b0f-456bbaf66508" xlink:to="loc_us-gaap_EarningsPerShareAbstract_019ca039-136e-728c-9fa7-486c75f6f949" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019ca039-136e-7599-8085-e51be728d798" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019ca039-136e-728c-9fa7-486c75f6f949" xlink:to="loc_us-gaap_EarningsPerShareBasic_019ca039-136e-7599-8085-e51be728d798" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019ca039-136e-773c-a3b4-14cfb5733e35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019ca039-136e-728c-9fa7-486c75f6f949" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019ca039-136e-773c-a3b4-14cfb5733e35" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.coremt.com/role/ScheduleIIDetails" xlink:type="simple" xlink:href="cmt-20251231.xsd#ScheduleIIDetails"/>
  <link:definitionLink xlink:role="http://www.coremt.com/role/ScheduleIIDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_019ca039-136e-728f-9d38-0487b57e5cf3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ValuationAndQualifyingAccountsDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_019ca039-136e-78f7-84bb-f85509ac35db" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ValuationAndQualifyingAccountsDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_019ca039-136e-728f-9d38-0487b57e5cf3" xlink:to="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_019ca039-136e-78f7-84bb-f85509ac35db" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_019ca039-136e-71ec-9d5e-7928d9e28d53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_019ca039-136e-78f7-84bb-f85509ac35db" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_019ca039-136e-71ec-9d5e-7928d9e28d53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_019ca039-136e-71ec-9d5e-7928d9e28d53_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_019ca039-136e-71ec-9d5e-7928d9e28d53" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_019ca039-136e-71ec-9d5e-7928d9e28d53_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_019ca039-136e-7cd2-bd5f-d6fdedb522aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_019ca039-136e-71ec-9d5e-7928d9e28d53" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_019ca039-136e-7cd2-bd5f-d6fdedb522aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForCreditLossMember_019ca039-136e-7be2-a224-6684edac338f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForCreditLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_019ca039-136e-7cd2-bd5f-d6fdedb522aa" xlink:to="loc_us-gaap_AllowanceForCreditLossMember_019ca039-136e-7be2-a224-6684edac338f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cmt_SECSchedule1209AllowanceChargebacksMember_019ca039-136e-743f-bf83-9b640a6aa317" xlink:href="cmt-20251231.xsd#cmt_SECSchedule1209AllowanceChargebacksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_019ca039-136e-7cd2-bd5f-d6fdedb522aa" xlink:to="loc_cmt_SECSchedule1209AllowanceChargebacksMember_019ca039-136e-743f-bf83-9b640a6aa317" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019ca039-136e-71d0-8d1e-8b5c965f443e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MovementInValuationAllowancesAndReservesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_019ca039-136e-728f-9d38-0487b57e5cf3" xlink:to="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019ca039-136e-71d0-8d1e-8b5c965f443e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_019ca039-136e-7a56-9141-bce0cc42fb04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019ca039-136e-71d0-8d1e-8b5c965f443e" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesBalance_019ca039-136e-7a56-9141-bce0cc42fb04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_019ca039-136e-7064-aced-7ce94de084eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019ca039-136e-71d0-8d1e-8b5c965f443e" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_019ca039-136e-7064-aced-7ce94de084eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_019ca039-136e-7da5-9a8c-4698a562b78a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019ca039-136e-71d0-8d1e-8b5c965f443e" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_019ca039-136e-7da5-9a8c-4698a562b78a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDeductions_019ca039-136e-7519-a53b-f567988a4f25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesDeductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019ca039-136e-71d0-8d1e-8b5c965f443e" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDeductions_019ca039-136e-7519-a53b-f567988a4f25" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_019ca039-136e-7dfb-a8d7-c430c9d184fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent" xlink:type="arc" order="41"/>
  </link:definitionLink>
</link:linkbase>
