A local mixed valence model

We consider a purely electronic model for local valence fluctuations consisting of a spinless localized 4f-level interacting with spinless extended 5d-states. We show that (a) the impurity model is related to the anisotropic Kondo problem, (b) a single 4f-level behaves like a resonant level with temperature-dependent width and (c) these results, when extended to a concentrated system of local incoherent mixed valence levels, are qualitatively in agreement with the main experimental features for mixed valence compounds.