  The dynamical spin susceptibility is studied in the magnetically-disordered
phase of heavy-Fermion systems near the antiferromagnetic quantum phase
transition. In the framework of the $S=1/2$ Kondo lattice model, we introduce a
perturbative expansion treating the spin and Kondo-like degrees of freedom on
an equal footing. The dynamical spin susceptibility displays a two-component
behaviour in agreement with the inelastic neutron scattering (INS) experiments
performed in $CeCu_{6}$, $Ce_{1-x}La_{x}Ru_{2}Si_{2}$ and $UPt_{3}$: a
quasielastic q-independent peak as in a Fermi liquid theory, and a strongly
q-dependent inelastic peak typical of a non-Fermi liquid behaviour. Very
strikingly, the position of the inelastic peak is found to be pushed to zero at
the antiferromagnetic transition. The picture is consistent with the neutron
cross sections observed in INS experiments.
