Flavor-changing signatures of spacetime-symmetry violations

This proceedings contribution discusses Lorentz and CPT violation in the context of charged-lepton flavor-changing processes. Particular emphasis is placed on coherent muon-to-electron conversion in muonic atoms. Data collected by the SINDRUM~II experiment at the Paul Scherrer Institute is used to extract constraints on mass dimension $d=5$ electromagnetic and $d=6$ quark-lepton effects. The Mu2e experiment at Fermilab and COMET experiment at the Japan Proton Accelerator Complex are projected to improve constraints by up to two orders in magnitude.