<?xml version='1.0' encoding='US-ASCII'?><schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:ubsprr="http://ubsprr/20260630" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:srt-types="http://fasb.org/srt-types/2025" xmlns:deprecated="http://www.xbrl.org/2009/role/deprecated" xmlns:dtr="http://www.xbrl.org/2009/dtr" xmlns:oef="http://xbrl.sec.gov/oef/2025" xmlns:ref="http://www.xbrl.org/2006/ref" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:oef-pre="http://xbrl.sec.gov/oef-pre/2025" xmlns:oef-lab="http://xbrl.sec.gov/oef-lab/2025" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:country="http://xbrl.sec.gov/country/2025" xmlns:us-roles="http://fasb.org/us-roles/2025" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:us-types="http://fasb.org/us-types/2025" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2022-03-31" xmlns:oef-def="http://xbrl.sec.gov/oef-def/2025" xmlns:negated="http://www.xbrl.org/2009/role/negated" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:srt="http://fasb.org/srt/2025" xmlns:oef-sr="http://xbrl.sec.gov/oef-sr/2025" xmlns:srt-roles="http://fasb.org/srt-roles/2025" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrli="http://www.xbrl.org/2003/instance" targetNamespace="http://ubsprr/20260630" elementFormDefault="qualified"><import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/><import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/><import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd"/><import namespace="http://fasb.org/us-types/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-types-2025.xsd"/><import namespace="http://www.xbrl.org/dtr/type/2022-03-31" schemaLocation="https://www.xbrl.org/dtr/type/2022-03-31/types.xsd"/><import namespace="http://xbrl.sec.gov/country/2025" schemaLocation="https://xbrl.sec.gov/country/2025/country-2025.xsd"/><import namespace="http://fasb.org/srt/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd"/><import namespace="http://fasb.org/srt-types/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-types-2025.xsd"/><import namespace="http://xbrl.sec.gov/oef-sr/2025" schemaLocation="https://xbrl.sec.gov/oef/2025/oef-sr-2025.xsd"/><import namespace="http://fasb.org/us-gaap/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd"/><import namespace="http://fasb.org/us-roles/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd"/><import namespace="http://fasb.org/srt-roles/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-roles-2025.xsd"/><annotation><appinfo><link:linkbase id="lnk"><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://xbrl.sec.gov/oef/role/ShareholderReport" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#ShareholderReport"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/ShareholderReportHoldingsDetails" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#ShareholderReportHoldingsDetails"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/ShareholderReportLineGraphDetails" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#ShareholderReportLineGraphDetails"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/ShareholderReportAverageAnnualReturnDetails" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#ShareholderReportAverageAnnualReturnDetails"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/ClassOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#ClassOnly"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/BroadBasedIndexOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#BroadBasedIndexOnly"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/AdditionalIndexOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#AdditionalIndexOnly"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/LargestHoldingOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#LargestHoldingOnly"/><link:roleRef roleURI="http://xbrl.sec.gov/oef/role/Other1CategoryOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#Other1CategoryOnly"/><link:presentationLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ShareholderReport"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_ShareClassDomain" xlink:label="ShareClassDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000232065Member" xlink:label="C000232065Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000232065Member" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000246508Member" xlink:label="C000246508Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000246508Member" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/></link:presentationLink><link:presentationLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ShareholderReportHoldingsDetails"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_ShareClassDomain" xlink:label="ShareClassDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000232065Member" xlink:label="C000232065Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000232065Member" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000246508Member" xlink:label="C000246508Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000246508Member" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_LargestHoldingsDomain" xlink:label="LargestHoldingsDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" xlink:label="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="LargestHoldingsDomain" xlink:to="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" order="3.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" order="4.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" order="5.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_OtherCategory1Domain" xlink:label="OtherCategory1Domain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_AMinus1PlusCTIMember" xlink:label="AMinus1PlusCTIMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="OtherCategory1Domain" xlink:to="AMinus1PlusCTIMember" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/></link:presentationLink><link:presentationLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ShareholderReportLineGraphDetails"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_ShareClassDomain" xlink:label="ShareClassDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000232065Member" xlink:label="C000232065Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000232065Member" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000246508Member" xlink:label="C000246508Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000246508Member" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_BroadBasedIndexDomain" xlink:label="BroadBasedIndexDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="BroadBasedIndexDomain" xlink:to="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="BroadBasedIndexDomain" xlink:to="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_AdditionalIndexDomain" xlink:label="AdditionalIndexDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="AdditionalIndexDomain" xlink:to="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="AdditionalIndexDomain" xlink:to="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/></link:presentationLink><link:presentationLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ShareholderReportAverageAnnualReturnDetails"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_ShareClassDomain" xlink:label="ShareClassDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000232065Member" xlink:label="C000232065Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000232065Member" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000246508Member" xlink:label="C000246508Member"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ShareClassDomain" xlink:to="C000246508Member" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/label" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_BroadBasedIndexDomain" xlink:label="BroadBasedIndexDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="BroadBasedIndexDomain" xlink:to="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="BroadBasedIndexDomain" xlink:to="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_AdditionalIndexDomain" xlink:label="AdditionalIndexDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="AdditionalIndexDomain" xlink:to="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" order="1.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember"/><link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="AdditionalIndexDomain" xlink:to="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" order="2.0" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" priority="1"/></link:presentationLink><link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ClassOnly"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_ShareClassDomain" xlink:label="ShareClassDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000232065Member" xlink:label="C000232065Member"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareClassDomain" xlink:to="C000232065Member" order="1.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000246508Member" xlink:label="C000246508Member"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareClassDomain" xlink:to="C000246508Member" order="2.0" priority="1"/></link:definitionLink><link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/BroadBasedIndexOnly"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_BroadBasedIndexDomain" xlink:label="BroadBasedIndexDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BroadBasedIndexDomain" xlink:to="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" order="1.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BroadBasedIndexDomain" xlink:to="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" order="2.0" priority="1"/></link:definitionLink><link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/AdditionalIndexOnly"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_AdditionalIndexDomain" xlink:label="AdditionalIndexDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AdditionalIndexDomain" xlink:to="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" order="1.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AdditionalIndexDomain" xlink:to="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" order="2.0" priority="1"/></link:definitionLink><link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/LargestHoldingOnly"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_LargestHoldingsDomain" xlink:label="LargestHoldingsDomain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" order="1.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" order="2.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" xlink:label="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LargestHoldingsDomain" xlink:to="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" order="3.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" order="4.0" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LargestHoldingsDomain" xlink:to="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" order="5.0" priority="1"/></link:definitionLink><link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/Other1CategoryOnly"><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2025/oef-2025.xsd#oef_OtherCategory1Domain" xlink:label="OtherCategory1Domain"/><link:loc xlink:type="locator" xlink:href="#ubsprr_AMinus1PlusCTIMember" xlink:label="AMinus1PlusCTIMember"/><link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="OtherCategory1Domain" xlink:to="AMinus1PlusCTIMember" order="1.0" priority="1"/></link:definitionLink><link:labelLink xlink:type="extended" xlink:role="http://www.xbrl.org/2003/role/link"><link:loc xlink:type="locator" xlink:href="#ubsprr_C000232065Member" xlink:label="C000232065Member"/><link:label xlink:type="resource" xlink:label="label_C000232065Member" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">C000232065</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="C000232065Member" xlink:to="label_C000232065Member" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_C000246508Member" xlink:label="C000246508Member"/><link:label xlink:type="resource" xlink:label="label_C000246508Member" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">C000246508</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="C000246508Member" xlink:to="label_C000246508Member" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember"/><link:label xlink:type="resource" xlink:label="label_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xml:lang="en-US">UBS Index: Bloomberg US Aggregate Bond Index</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:to="label_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" priority="1"/><link:label xlink:type="resource" xlink:label="label_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember_28598" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">UBS Index: Bloomberg US Aggregate Bond Index_28598</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" xlink:to="label_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember_28598" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:label="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember"/><link:label xlink:type="resource" xlink:label="label_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xml:lang="en-US">UBS Index: Bloomberg US Aggregate Bond Index</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:to="label_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" priority="1"/><link:label xlink:type="resource" xlink:label="label_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember_28597" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">UBS Index: Bloomberg US Aggregate Bond Index_28597</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" xlink:to="label_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember_28597" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember"/><link:label xlink:type="resource" xlink:label="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xml:lang="en-US">UBS Index: ICE BofA 3 Month US Treasury Bill Index</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:to="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" priority="1"/><link:label xlink:type="resource" xlink:label="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember_28598" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">UBS Index: ICE BofA 3 Month US Treasury Bill Index_28598</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" xlink:to="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember_28598" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:label="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember"/><link:label xlink:type="resource" xlink:label="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xml:lang="en-US">UBS Index: ICE BofA 3 Month US Treasury Bill Index</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:to="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" priority="1"/><link:label xlink:type="resource" xlink:label="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember_28597" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">UBS Index: ICE BofA 3 Month US Treasury Bill Index_28597</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" xlink:to="label_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember_28597" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember"/><link:label xlink:type="resource" xlink:label="label_FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">Federal Home Loan Bank Discount NotesFR_313385YU4_0.010000_2026-07-01</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" xlink:to="label_FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember"/><link:label xlink:type="resource" xlink:label="label_FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">Federal Home Loan Bank Discount NotesFR_313385B88_0.010000_2026-08-14</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" xlink:to="label_FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" xlink:label="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember"/><link:label xlink:type="resource" xlink:label="label_FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">Federal Farm Credit Discount NotesFR_313313YU6_0.010000_2026-07-01</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" xlink:to="label_FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember"/><link:label xlink:type="resource" xlink:label="label_FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">Federal Home Loan Bank Discount NotesFR_313385ZC3_0.010000_2026-07-09</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" xlink:to="label_FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" xlink:label="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember"/><link:label xlink:type="resource" xlink:label="label_FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">Federal Home Loan Bank Discount NotesFR_313385A97_0.010000_2026-08-07</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" xlink:to="label_FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" priority="1"/><link:loc xlink:type="locator" xlink:href="#ubsprr_AMinus1PlusCTIMember" xlink:label="AMinus1PlusCTIMember"/><link:label xlink:type="resource" xlink:label="label_AMinus1PlusCTIMember" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">A-1+</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AMinus1PlusCTIMember" xlink:to="label_AMinus1PlusCTIMember" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_NoTradingSymbolFlag" xlink:label="NoTradingSymbolFlag"/><link:label xlink:type="resource" xlink:label="label_NoTradingSymbolFlag" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">No Trading Symbol [Flag]</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="NoTradingSymbolFlag" xlink:to="label_NoTradingSymbolFlag" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsNet" xlink:label="AssetsNet"/><link:label xlink:type="resource" xlink:label="label_AssetsNet" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">AssetsNet</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="AssetsNet" xlink:to="label_AssetsNet" priority="1"/><link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentCompanyPortfolioTurnover" xlink:label="InvestmentCompanyPortfolioTurnover"/><link:label xlink:type="resource" xlink:label="label_InvestmentCompanyPortfolioTurnover" xlink:role="http://www.xbrl.org/2003/role/label" xml:lang="en-US">InvestmentCompanyPortfolioTurnover</link:label><link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="InvestmentCompanyPortfolioTurnover" xlink:to="label_InvestmentCompanyPortfolioTurnover" priority="1"/></link:labelLink></link:linkbase></appinfo></annotation><element name="C000232065Member" id="ubsprr_C000232065Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="C000246508Member" id="ubsprr_C000246508Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" id="ubsprr_UBSIndexBloombergUSAggregateBondIndex28598BroadBasedIndexMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" id="ubsprr_UBSIndexBloombergUSAggregateBondIndex28597BroadBasedIndexMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" id="ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28598AdditionalIndexMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" id="ubsprr_UBSIndexICEBofA3MonthUSTreasuryBillIndex28597AdditionalIndexMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" id="ubsprr_FederalHomeLoanBankDiscountNotesFR313385YU400100002026Minus07Minus01CTIMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" id="ubsprr_FederalHomeLoanBankDiscountNotesFR313385B8800100002026Minus08Minus14CTIMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" id="ubsprr_FederalFarmCreditDiscountNotesFR313313YU600100002026Minus07Minus01CTIMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" id="ubsprr_FederalHomeLoanBankDiscountNotesFR313385ZC300100002026Minus07Minus09CTIMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" id="ubsprr_FederalHomeLoanBankDiscountNotesFR313385A9700100002026Minus08Minus07CTIMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/><element name="AMinus1PlusCTIMember" id="ubsprr_AMinus1PlusCTIMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration"/></schema>
