NEUTRON DIFFRACTION STUDIES OF HYBRIDIZATION AND ANISOTROPY IN URANIUM INTERMETALLIC COMPOUNDS. R. A. Robinson, Los Alamos National Laboratory, Los Alamos, NM 87545

We discuss the application of powder and single-crystal neutron diffraction techniques to the problem of hybridization between the uranium f-electrons and transition-metal d-electrons in uranium intermetallics. In recent years, a simple phenomenological picture has emerged in which the magnetic anisotropy is closely related to the bonding anisotropy and by inference, anisotropy in the hybridization. As a rule, the uranium moments tend to lie perpendicular to directions or planes containing nearest uranium neighbours. While this works very well in most cases studied to date, a few exceptions are beginning to emerge. Most notable are the cases of the noncollinear antiferromagnets UPdSn (space group P6₃mc) and UNiGe (space group Pnma), which have been studied using a battery of neutron techniques (powder, Rietveld refinement, single crystal at spallation source and reactor, polarised neutrons, measurements in horizontal and vertical fields), as well as the complementary technique of bulk high-field magnetization. Symmetry techniques (Shubnikov groups and Irreducible representations) have also been heavily exploited and we will discuss their application to this problem, particularly the magnetic implementation in the Rietveld package, GSAS.