Pressure-induced Americium Valence Fluctuations Revealed by Electrical Resistivity

Electrical resistivity of americium-plutonium fcc alloys was studied over a series of high-pressure¿induced structural phase transitions accompanied by a volume collapse. The temperature dependence of resistivity flattens progressively in the high-pressure phases pointing to the presence of random strong scatterers at the Fermi energy. A theoretical analysis shows that this development is not related to the expected simple delocalization of Am 5f states. Instead it points to pressure-induced americium valence fluctuations (5f6-5f7), which provides a new microscopic basis for the understanding of transuranium materials on the verge of localization of the 5f electronic states.JRC.E.6-Actinides researc