Electron-polaron effects in compounds with an unstable f-shell
Kikoin K. A. , Khomskii D. I.
The appearance of a mixed valence and of heavy fermions is linked with features of the intratomic structure of elements with an unstable/shell. The double electron-polaron effect which arises here in the conduction band and in the/-electron cores can cause an anomalous increase in the state density at the Fermi level.