i)  I have been trying to understand the optical anomalies at the  valence transition in YbInCu$_4$ and EuNi(Si$_x$Ge$_{1-x}$)$_2$-like intermetallics, using the Falicov-Kimball model.

ii) I also tried to understand the phase diagram of heavy fermions and valence-fluctuators,  like CeCu(2)(Si(x)Ge(1-x))2, CeRu(2)(Si(x)Ge(1-x))2 , or EuCu(2)(Si(x)Ge(1-x))2,  obtained by pressure and doping experiments. A biased look at  the data shows that above some pressure the nature of the AFM changes: the large f-moments of the low-pressure AFM phase become very small in the high-pressure AFM phase. The 'poor man's solution' of the periodic Anderson model indicates that as pressure is reduced, the usual transition from the Fermi liquid state to the AFM state with  screened local moments is followed by another transition (or crossover) at which the local moments 'undress' and the AFM state has unscreened moments only.