  We propose a Theoretical model accounting for the recently observed reduced
magnetic moment of Gadolinium in fullerenes. While this reduction has been
observed also for other trivalent rare-hearth atoms (Dy3+, Er3+, Ho3+) in
fullerenes and can be ascribed to crystal field effects, the explanation of
this phenomena for Gd3+ is not straightforward due to the sphericity of its
ground state (S=7/2, L=0). In our model the momentum lowering is the result of
a subtle interplay between hybridisation and spin-orbit interaction.
