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. Sin ce 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 prepa red cross-junctions consisting of a UPd2Al3 base electrode and a metal counter electrode (Au, Al or Ag). These small area contacts without a rtificial barriers have only low junction resistances and suffer from irreproducibility. On the other hand, on some of those junctions we ob served BCS-like tunneling conductivity. In order to increase the junct ion 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.