FURTHER EVIDENCE FOR TIME-REVERSAL SYMMETRY-BREAKING IN THE HEAVY-ELECTRON SUPERCONDUCTOR UPT3

A 2D electron gas Hall probe was used to measure the local magnetic in duction B(H,T) of the heavy-electron superconductor UPt3 below T-c. We interpret these results to imply the formation of a spontaneous magne tization, broken into domains for applied fields greater than H-c1. Th is is in agreement with recent mu SR results, which suggested the appe arance of an inhomogeneous magnetization in applied fields in addition to the spontaneous magnetization that was observed in zero applied fi elds. Taken together, this suggests that the low-temperature supercond ucting state of UPt3 is unconventional and of odd parity.