Underscreened Kondo lattice model at finite temperature

We have developed an underscreened Kondo lattice model with an intra-site Kondo exchange interaction JK between the conduction band and localized 5f electrons-described by S=1 spins in the f2 configuration-and an inter-site ferromagnetic exchange f-f interaction JH. Using a fermionic representation for the spin operators and a mean-field approximation we obtain, from T=0 up to a critical temperature, a Kondo-ferromagnetic coexistence. This is in agreement with the experimental situation of some Uranium compounds, such as UTe or UCu0.9Sb2, which order ferromagnetically with a Curie temperature of order 100K and present also a Kondo behavior. The Curie and Kondo temperatures are also determined