  We study the low-temperature properties of a Kondo lattice using the large-N
formalism. For a singular density of conduction states (DOS), we generalize the
single-impurity result of Withoff and Fradkin: the strong-coupling fixed point
becomes irrelevant if the DOS vanishes at the Fermi level E_F. However, for E_F
close enough to the singularity, and close to half-filling, the Kondo
temperature, $T_K$, can become much smaller than the characteristic Fermi
liquid scale. At T=0, a meta-magnetic transition occurs at the critical
magnetic field H_c ~ (k_B/mu_B) T_K. Our results provide a qualitative
explanation for the behavior of the YbInCu_4 compound below the valence-change
transition.
