QUANTUM OSCILLATION MEASUREMENTS OF BAND MAGNETISM IN UPT3 AND CERU2SI2

A central enigma of the heavy fermion metals is the dual behaviour of the f electrons which, at relatively short time scales, exhibit the pr operties expected of well-localised moments and, at very long time sca les, in cooperation with other valence electrons at low temperatures, display the characteristics of massive itinerant carriers having a sha rply defined Fermi surface. Detailed experimental support for the latt er (long-time) cooperative behaviour of f electrons in UPt3 and CeRu2S i2 has been furnished principally by studies of quantum oscillatory ph enomena. In this paper the information provided by these studies is su mmarised, and recent observations of the evolution of the quasiparticl e band structure during the magnetisation process and at the metamagne tic transitions in these materials are described.