Intermediate valence of plutonium chalcogenides as determined by photoemission

There has been considerable experimental evidence, like magnetism, electrical conductivity, specific heat, lattice constant, elasticity and compressibility, showing that the plutonium monochalcogenides are intermediate valent and thus were the first actinide compounds where this aspect could be experimentally verified. Also, theoretical calculations confirm the experimental findings. Recently, photoemission has been performed on PuSe layers and PuTe single crystals and the findings have been interpreted as a 5f localization and not an intermediate valent configuration where 5f and 6d states hybridize. In this paper, it will be shown that also these photoemission data give direct evidence of intermediate valence. However, in addition, a narrow 5f band is observed at the Fermi level, causing the observed strongly enhanced Pauli paramagnetism.