5f states in the Pauli paramagnet UB2 and in the heavy fermion antiferromagnetic superconductor UPt3 from XANES and XMCD

The aim of this proposal is to record with high accuracy XANES and XMCD spectra at the U-M4,5 edges in UB2 and UPt3.In addition we will also record spectra at the Pt-L2,3 edges in UPt3. XANES spectra the U-M4,5 edges will provide the branching ratio of the white lines and the expectation value of the angular part of the spin-orbit interaction the 5f states.Their values rely on the coupling scheme (intermediate or LS), the 5f electron count and their localization. XMCD data will allow to determinate the U-5f and Pt-5d orbital and spin moments and their ratios. Those information will give further indications on the number of 5f electrons and their delocalization. It is worth to emphasize that the 5f count in uranium intermetallics is in general controversial. Its knowledge is an essential piece of information for modeling their electronic structure.