  We report the temperature-pressure-magnetic field phase diagram made from
electrical resistivity measurements for the ferromagnetic (FM) Kondo lattice
CeRuPO. The ground state at zero field changes from the FM state to another
state, which is suggested to be an antiferromagnetic (AFM) state, above ~0.7
GPa, and the magnetically ordered state is completely suppressed at ~2.8 GPa.
In addition to the collapse of the AFM state under pressure and a magnetic
field, a metamagnetic (MM) transition from a paramagnetic state to a polarized
paramagnetic state appears. CeRuPO will give us a rich playground for
understanding the mechanism of the MM transition under comparable FM and AFM
correlations in the Kondo lattice.
