UC Irvine

The high-temperature structural phase transition in URe2 is only moderately influenced by thorium impurities at low concentrations but disappears rapidly when the thorium content exceeds 25%. Replacing thorium in ThRe2 by uranium reduces its critical temperature for the onset of superconductivity but much less drastically than do uranium impurities in metallic thorium. A comparison of the low-temperature specific heats of URe2 and ThRe2 indicates that the density of f-electron states at the Fermi energy EF in URe2 is not large and that the f electrons in URe2 behave similarly to d electrons in non-magnetic d transition metals. © 1986.