Using muon spin rotation at the Swiss Muon Source SmS, researchers at the Paul Scherrer Institute (PSI) have discovered that a quantum phenomenon known as time-reversal symmetry breaking occurs at the surface of the Kagome superconductor RbV3Sb5 at temperatures as high as 175 K. This sets a new record for the temperature at which time-reversal symmetry breaking is observed among Kagome systems.