Anisotropy of the Josephson critical current between UPt3 and Nb

Josephson critical current densities J(c) between a single crystal UPt3 and an s-wave superconductor have been investigated for UPt3-Cu-Nb junctions a nd 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 p arallel 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 superconductivi ty of UPt3.