We infer that soft-x-ray absorption spectroscopy is a versatile method for
the determination of the crystal-field ground state symmetry of rare earth
Heavy Fermion systems, complementing neutron scattering. Using realistic and
universal parameters, we provide a theoretical mapping between the polarization
dependence of Ce M4,5 spectra and the charge distribution of the Ce 4f
states. The experimental resolution can be orders of magnitude larger than the
4f crystal field splitting itself. To demonstrate the experimental
feasibility of the method, we investigated CePd2Si2, thereby settling an
existing disagreement about its crystal-field ground state