Abstract
Point-contact spectroscopy, via the mechanism of Andreev reflection between a normal metal and a superconductor, can be employed to obtain information about the superconductive energy gap. In the present work, point-contacts between the heavy-fermion superconductor UPt3 and Pt have been studied down to 36 mK and in magnetic fields up to 6 T. Andreev reflection is observed only in the low-field, low-temperature superconducting phase. The unusual temperature and magneticfield dependence together with the gap anisotropy give direct experimental evidence that the different superconductive phases in UPt3 have distinctly different order parameters.
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