  Magnetic properties of uranium and neptunium compounds showing the
coexistence of Kondo screening effect and ferromagnetic order are investigated
within the Anderson lattice Hamiltonian with a two-fold degenerate $f$-level in
each site, corresponding to $5f^2$ electronic configuration with $S=1$ spins. A
derivation of the Schrieffer-Wolff transformation is presented and the
resulting Hamiltonian has an effective $f$-band term, in addition to the
regular exchange Kondo interaction between the $S=1$ $f$-spins and the $s=1/2$
spins of the conduction electrons. The obtained effective Kondo lattice model
can describe both the Kondo regime and a weak delocalization of $5f$-electron.
Within this model we compute the Kondo and Curie temperatures as a function of
model parameters, namely the Kondo exchange interaction constant $J_K$, the
magnetic intersite exchange interaction $J_H$ and the effective $f$-bandwidth.
We deduce, therefore, a phase diagram of the model which yields the coexistence
of Kondo effect and ferromagnetic ordering and also accounts for the pressure
dependence of the Curie temperature of uranium compounds such as UTe.
