Search for superconducting energy gap in UPt₃ by point-contact spectroscopy

We have investigated the differential resistance of the point contacts between heavy-fermion superconductor UPt₃ and a normal metal Pt, which were fabricated using a commercial piezo-electric actuator, and retried the observation of the energy gap of UPt₃. A V-shaped dip is observed in both normal and superconducting states and disappeared around T_K ∼ 20 K, suggesting that it is related to the Kondo effect. Below the superconducting transition temperature, a shallow double-minimum structure, which indicates the energy gap, has been observed for the contacts on the faces perpendicular to the a-, b- and c-axes of UPt₃.