Heavy Electron Behavior in the System UPd_2−XAu_XSn (0 ≤ x ≤2)

Abstract

New interest in the family of Heusler alloys (cubic L2₁ structure)has been generated by the recent discovery of superconductivity in several of its members such as RPd₂Sn (R = Sc, Y, Tm, Yb, Lu), ¹ YPd₂M (M = Pb, In, Sb)² as well as coexistence of superconductivity and antiferromagnetism in YbPd₂Sn.^1,2 Previously, we reported that the compound UPd₂Sn, which crystallizes in a more complicated structure expected to be ortho rhombic, exhibits interesting heavy-electron properties.³ In particular, UPd₂Sn has an electronic specific heat coefficient γ of ∼80 mJ/mole U−K² and seems to behave like a Fermi liquid below 10 K as confirmed by the low temperature T² dependence of its electrical resistivity, the deviation of its magnetic susceptibility from a Curie-Weiss law below 10 K, and by a maximum at 10 K in the U-5f electronic specific heat δC/T vs T curve. The compound UPd₂Sn was compared, with respect to the Kondo lattice coherence regime, to materials like CeAl₃, CeCu₂Si₂ and CeCu₄Al₈. In this work, we report on the effects of chemical substitution in UPd₂Sn by studying the crystal structure and the temperature dependence of the electrical resistivity ρ(T), the magnetic susceptibility χ(T) and the specific heat C(T) of the series UPd_2−xAu_X Sn (0 ≤ x ≤ 2).