Anisotropy of the Josephson Critical Current between UPt₃ and Nb

Josephson critical current densities Jc between a single crystal UPt₃ and an s-wave superconductor have been investigated for UPt₃-Cu-Nb junctions and UPt₃-Nb junctions. The anisotropic temperature dependence is observed at about the lower critical temperature T^-_c of UPt₃; the increase in J_c with decreasing temperatures becomes fast below T^-_c for a current flow parallel to the crystallographic c axis and it becomes rather slow below T^-_c for a current flow parallel to the b axis. This anisotropy gives clear evidence that the Josephson effect reflects the anisotropic superconductivity of UPt₃.