PROBING THE SUPERCONDUCTING STATE OF UPD2AL3 THIN-FILMS BY TUNNELING SPECTROSCOPY

Giaever-type planar cross junctions of thin films of the heavy fermion superconductor UPd2Al3 and counter-electrodes of Au, Ag and Al were p repared. Tunneling barriers consisting of the native oxide layer of UP d2Al3 and artificial barriers of AlOx and UOx were investigated. The j unctions without artificial barrier show a lack of reproducebility On some junctions a BCS-like tunneling conductivity with a ratio of 2 Del ta(0)/k(B)T(c) similar or equal to 3.8 was observed. Using oxidized Al deposited at room temperature as a barrier no substantial increase of the junction resistance occured. With Uraniumoxide a much higher resi stance was obtained, but an association of the bias dependent junction conductivity with density of states effects was not possible up to no w.