A search for the nonresonant <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msubsup><a:mi mathvariant="normal">Λ</a:mi><a:mi>c</a:mi><a:mo>+</a:mo></a:msubsup><a:mo stretchy="false">→</a:mo><a:mrow><a:mi>p</a:mi><a:mrow><a:msup><a:mi>μ</a:mi><a:mo>+</a:mo></a:msup><a:msup><a:mi>μ</a:mi><a:mo>−</a:mo></a:msup></a:mrow></a:mrow></a:math> decay is performed using proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the LHCb experiment, corresponding to an integrated luminosity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>5.4</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mi>fb</e:mi><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:math>. No evidence for the decay is found in the dimuon invariant-mass regions where the expected contributions of resonances is subdominant. The upper limit on the branching fraction of the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msubsup><g:mi mathvariant="normal">Λ</g:mi><g:mi>c</g:mi><g:mo>+</g:mo></g:msubsup><g:mo stretchy="false">→</g:mo><g:mrow><g:mi>p</g:mi><g:mrow><g:msup><g:mi>μ</g:mi><g:mo>+</g:mo></g:msup><g:msup><g:mi>μ</g:mi><g:mo>−</g:mo></g:msup></g:mrow></g:mrow></g:math> decay is determined to be <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:mn>2.9</k:mn><k:mo stretchy="false">(</k:mo><k:mn>3.2</k:mn><k:mo stretchy="false">)</k:mo><k:mo>×</k:mo><k:msup><k:mrow><k:mn>10</k:mn></k:mrow><k:mrow><k:mo>−</k:mo><k:mn>8</k:mn></k:mrow></k:msup><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mtext>at</k:mtext><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mn>90</k:mn><k:mo>%</k:mo><k:mo stretchy="false">(</k:mo><k:mn>95</k:mn><k:mo>%</k:mo><k:mo stretchy="false">)</k:mo></k:mrow></k:math> confidence level. The branching fractions in the dimuon invariant-mass regions dominated by the <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mi>η</q:mi></q:math>, <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mi>ρ</s:mi></s:math> and <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:mi>ω</u:mi></u:math> resonances are also determined. © 2024 CERN, for the LHCb Collaboration 2024 CERN