Coherence scale of the Kondo lattice

It is shown that the large-N approach yields two energy scales for the Kond o lattice model. The single-impurity Kondo temperature, T-K, signals the on set of local singlet formation, while Fermi-liquid coherence sets in only b elow a lower scale, T*. At low conduction electron density n(c) ("exhaustio n" limit), the ratio T*/T-K is much smaller than unity, and is shown to dep end only on n(c) and not on the Kondo coupling. The physical meaning of the se two scales is demonstrated by computing several quantities as a function of n(c) and temperature.