  In a model system with three S=1 pseudo-spins situated in an anisotropic mean
field we compute the thermodynamic response in a self consistent manner. An
adhoc uniform broadening of all energy levels of the (localized) spins due to
their interaction with conduction electrons is introduced. The results with a
minimal set of parameters reproduce with remarkable fidelity the properties of
the strongly correlated metamagnets UPt$_3$ and CeRu$_2$Si$_2$. Several key
predictions are made for further experimental confirmation.
