U DOPING STUDY OF U-BASED HEAVY FERMIONS - UCU4PD AND UCU3.5PD1.5

Effects of substituting La, Y, and Th for U (up to 20%) in UCu4Pd and UCu3.5Pd1.5 have been studied Via magnetic susceptibility, low tempera ture specific heat, and electrical resistivity. These two heavy fermio n compounds, identified previously as candidates for non-Fermi-liquid ground states, have markedly different response to alloying. A partial replacement of U by an element M in UCu4Pd results in a decrease in t he low temperature specific heat, normalized to a mole of U, independe ntly of the size and chemical nature of M. The alloying-caused changes in the specific heat and magnetic susceptibility Of UCu3.5Pd1.5 can b e correlated with hybridization strength as measured by U-Cu or U-Pd d istance.