Tunneling junctions of the heavy-fermion superconductor UPd2Al3

Tunneling spectroscopy on planar Giaever-type junctions is a powerful tool for the investigation of the superconducting state of metals. Since it is possible to prepare high-quality epitaxial thin films of the heavy-fermion compound UPd2Al3, this method can be used to examine the energy gap of this presumably unconventional superconductor. We prepared cross-junctions consisting of a UPd2Al3 base electrode and a metal counter electrode (Au, Al or Ag). These small area contacts without artificial barriers have only low junction resistances and suffer from irreproducibility. On the other hand, on some of those junctions we observed BCS-like tunneling conductivity. In order to increase the junction resistances AlOx or UOx were used as a artificial barrier with Al as a counter-electrode. As an alternative to quasi-particle tunneling, the preparation of Josephson-junctions could be an easier approach. A supercurrent between a small In-dot and an UPd2Al3 film was observed. (C) 1998 Elsevier Science B.V. All rights reserved.