The Kondo effect to heavy fermions studied using the de Haas-van Alphen effect

In this paper, we briefly review some recent de Haas-van Alphen experiments on two contrasting types of heavy fermion/Kondo systems for varying concen trations x of the impurity ion, Ce or U. In both systems the Fermi surface is observed to vary continuously with x: in CexL1-xB6, the Ce ions behave a s Kondo impurities while in UxTh1-xBe13 they do not. In both systems, the f electrons are also found to contribute only partially to the Fermi surface volume, therefore raising questions concerning the applicability of Fermi liquid theory. (C) 2001 Elsevier Science B.V. All rights reserved.