interaction. In the case of $n_\mathrm{tot}=1$ or $3$, an important role is played by the ratio $U/\Delta$, where $\Delta=|\ep0-\ed0|$ is the charge-transfer energy, the separation in energy between the two electron orbitals. Two regimes can be distinguished:[@zsa] (a) for $\Delta$ smaller than $U$ the model is in the so-called [*Charge-Transfer*]{} (CT) regime, that is expected to capture the properties of intermediate to late transition-metal oxides. Nevertheless in these systems the non-local hybridizations become important and require the introduction of other terms in the Hamiltonian to be properly described. (b) For $\Delta$ larger than $U$ the model is in the [*Mott-Hubbard*]{} (MH) regime, which models the properties of early transition-metal oxides and heavy fermion systems, usually dominated by local physics. In this work we shall focus on this latter model regime and study the doping of a Mott insulator.

In the simplest sketch of this regime, the non-correlated band has a lower energy than the correlated one (which however is dispersive only because of the hybridization with the itinerant fermions). The latter band is in turn split by the Mott gap (see ). Similarly to the Kondo Insulating regime, a heavy fermion state is obtained upon finite doping as soon as 