ANISOTROPIC JOSEPHSON EFFECTS IN POINT CONTACTS BETWEEN THE HEAVY-FERMION SUPERCONDUCTOR URU2SI2 AND NB

Point contacts between the heavy-fermion superconductor URu(2)S(i)2 an d Nb are studied. A finite de Josephson current is found in contacts a ligned parallel to the a-b directions of URu2Si2 whereas it is absent in contacts aligned along the c direction. We attribute this extreme a nisotropy; of the Josephson current to an unconventional superconducti ng order parameter in URu2Si2, with a symmetry leading to destructive interference for Josephson currents along the c direction.