Resistance scaling of point contacts between heavy-fermion superconductors and tungsten

We investigated point contacts between a tungsten tip and the heavy-fermion superconductors CeCu2Si2, UPt3, URu2Si2, UNi2Al3, and UPd2Al3. A correlation between contact size, magnitude of the superconducting anomalies, and specific resistivity of the heavy-fermion superconductors suggests that these anomalies are mainly due to diffusive and thermal transport. The residual contact resistance can be described by a strongly enhanced Sharvin resistance, probably caused by both a badly conducting normal interface layer on the heavy-fermion side and strong ordinary reflection of ballistic electrons. (orig.)