Kondo alloys with non-Fermi liquid properties
A major issue and current topic of debate in the field of highly-correlated electron systems is the fundamental question whether these systems, in their normal state, may be described as simple Fermi liquids. For some heavy-electron (HE) compounds (e.g. UPt3) this seems indeed to be the appropriate picture. Specific-heat and resistivity data, supported by results of de Haas-van Alphen experiments may be well explained in this way, if strongly renormalized Fermi-liquid parameters are introduced. More recent experimental work has indicated, however, that several HE compounds and related alloys display quite remarkable properties, which may much less well be related with 'conventional' Fermi liquid behaviour. Problems with Fermi-liquid type descriptions of relevant data were met on different occasions, including materials like UCu5-xPdx for x = 1 and 1.5, CeCu5.9Au0.1, UxY1-xPd3 (x < 0.2), Th1-xUxRu2Si2 (x < 0.07), U1-xThxPd2Al3 (x > 0.4) and also UBe13. In these compounds a set of data of specific-heat, magnetic susceptibility, resistivity and optical measurements was found to be at variance with the usual temperature dependence expected for these quantities in Fermi-liquid-type systems (see Fig. 1.1).