OBSERVATION OF ANDREEV REFLECTIONS AND JOSEPHSON EFFECTS IN POINT CONTACTS BETWEEN CONVENTIONAL AND THE HEAVY-FERMION SUPERCONDUCTOR URU2SI2

We have measured the dV/dI vs. V characteristics of point contacts bet ween the heavy-fermion superconductor URu2Si2 and the conventional sup erconductors Zn and NbTi. Contacts between URu(2)Sl(2) and Zn behave l ike a superconductor-normal metal-superconductor junction with a thick normal layer in the heavy-fermion part of the contact and show Andree v-reflection type structures related to both the heavy-fermion and the conventional superconductors. In contrast, contacts between URu2Si2 a nd NbTi become superconducting at low bias currents. The data indicate that proximity induced superconductivity is important for the couplin g of the two types of superconductivity. With such contacts we also fa bricated a closed-loop setup with two NbTi contacts on a URu2Si2 sampl e, which showed SQUID oscillation in a small magnetic field.