s-f hybridization model of UBe13

We assume that in UBe13 the 5f/sub 5/2hyphen/GAMMA8 crystal-field level of U is filled and that the GAMMA7 (Kramer's doublet) lies exactly at the Fermi surface, so as to be half full. Resonant hybridization of the GAMMA7 state with the Be(2s)-U(7s) conduction band leads to a Lorentzian density-of-states peak at E/sub F/. Its width is 12 K and its peak height is approx.250 times that of the conduction band. This model explains the (normal-state) heat capacity, magnetic susceptibility, and nuclear-spin relaxation versus T. Curie-Weiss behavior is obtained even though no local moments are presumed. We show that the hybridization matrix elements are extremely anisotropic--being zero for conduction electrons having k along the cubic axes. It follows that the superconducting energy gap is also anisotropic in k space, and that the heat capacity below T/sub c/ can be explained with singlet pairing caused by phonon-mediated interactions. Two key experiments are proposed