ANDREEV SCATTERING IN THE ANISOTROPIC HEAVY-FERMION SUPERCONDUCTOR UPT3

Andreev reflection between a normal metal and a superconductor was emp loyed to investigate the superconducting order parameter of the heavy- fermion superconductor UPt3. In the present work, point-contact spectr a are compared with dV/dI curves calculated assuming different order-p arameter symmetries, and that the electrons are injected preferentiall y in the forward direction with an angular spread described by a cone. Various order-parameter structures are compared for nonideal interfac es of d-wave superconductors and different directions of current flow. The analysis favors a two-dimensional order parameter with an orbital part with a, line of nodes in the basal plane and point nodes along t he c axis.