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    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NameOfMajorCustomerDomain" xlink:to="ChartererCMember" xlink:title="definition: NameOfMajorCustomerDomain to ChartererCMember" order="3.0" />
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    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RelatedPartyTransactionLineItems" xlink:to="RelatedPartyTransactionManagementFees" xlink:title="definition: RelatedPartyTransactionLineItems to RelatedPartyTransactionManagementFees" order="2.0" />
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    <link:loc xlink:type="locator" xlink:href="icon-20260630.xsd#icon_RelatedPartyTransactionCapitalRaisingCommissionRate" xlink:label="RelatedPartyTransactionCapitalRaisingCommissionRate" xlink:title="RelatedPartyTransactionCapitalRaisingCommissionRate" />
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