UNDERSCREENED KONDO EFFECT - A 2 S=1 IMPURITY MODEL

The underscreened Kondo effect is studied within a model of two impuri ties S = 1 interacting with the conduction band and via an interimpuri ty coupling K (S) over right arrow(1).(S) over right arrow(2). Using a mean-field treatment of the bosonized Hamiltonian, we show that there is no phase transition, but a continuous crossover versus K from a no n-Kondo behavior to an underscreened Kondo one. For a small antiferrom agnetic coupling (K > 0), a completely asymmetric situation is obtaine d with one s = 1/2 component strongly screened by the Kondo effect and the other one almost free to yield indirect magnetism, which shows fi nally a possible coexistence between a Ruderman-Kittel-Kasuya-Yosida i nteraction and a local Kondo effect, as observed in Uranium compounds such as UPt3.