VALENCE INSTABILITY OF URANIUM IN U(AL1-XGEX)(3)

The electronic structure of U and Ge in the solid solutions U(Al1-xGex )(3) is investigated by measuring x-ray line shifts. It is shown that uranium has the mixed valence U3+ [Rn](5f(3))-U4+ [Rn](5f(2)) over the entire composition range (0 less than or equal to x less than or equa l to 1) and that the population of the uranium 5f shell increases by s imilar to 0.28 5f electrons/U atom from UAl3 (x=0) to UGe3 (x=1). The electronic structure of Ge is close to the electronic structure of Ge metal over the entire composition range 0<x less than or equal to 1. N o variation of the population of the Ge 4p shell is detected to within the experimental error (similar to 0.1 4p electrons/Ge atom) as the c omposition varies from x=0.2 to 1. It is established that the delocali zation of a U 5f electron occurs as a result of its transition to the s or d band of the same uranium atom. (C) 1997 American Institute of P hysics.