  The ground state properties of CeFePO, a homologue of the new high
temperature superconductors RFePnO(1-x)Fx, were studied by means of
susceptibility, specific heat, resistivity, and NMR measurements on
polycrystals. All the results demonstrate that this compound is a magnetically
non-ordered heavy Fermion metal with a Kondo temperature TK~10K, a Sommerfeld
coefficient gamma=700mJ/molK2 and a mass enhancement factor of the order of
200. The absence of a Fe-contribution to the effective moment at high
temperatures indicates that the magnetism in CeFePO is completely dominated by
the effect of Ce. Thus the strong electronic correlation effects originate from
the Ce-4f electrons rather than from the Fe-3d electrons. An enhanced
Sommerfeld-Wilson ratio R=5.5 as well as a Korringa product S0/T1TK2~0.065 well
below 1 indicate the presence of ferromagnetic correlations. Therefore, CeFePO
appears to be on the non-magnetic side of a ferromagnetic instability.

Strongly Correlated Electrons;Materials Science