Effect of the local charge disproportionation on the electronic structure of BaPb1-xBixO3

We calculate the electronic structure of BaPb1-xBixO3 within a simplified version of a model proposed before for the superconductivity, taking into account the local disproportionation of the Bi atoms in the coherent potential approximation. Three different regimes are obtained as a function of the Bi concentration x: normal metal, metallic with a pseudogap, and insulating phase. This allows a satisfactory explanation of the optical properties, resistivity, Hall, and Seebeck effects. The agreement is improved when the many-body effects due to the covalency of the Bi-O bonding, invoked for the pairing mechanism, are also considered.