2-BAND MODEL FOR KONDO INSULATORS - THERMODYNAMIC AND SCALING PROPERTIES

Recently a new family of heavy fermions (e.g., Ce3Bi4Pt3) has been dis covered which is characterized by an insulating ground state. Similar behavior has been found in some transition metal compounds like FeSi. We introduce a two-band model to describe the physical properties of t hese systems. Coulomb correlations in the narrow band are treated beyo nd the mean field approach. We find that a critical value of the hybri dization V(c) is required to open a gap that produces an insulating gr ound state. We discuss the scaling properties of these systems close t o V(c). The temperature-dependent magnetic susceptibility calculated i n our model is in good agreement with experimental results.