  Hill plot is a well-known criterion of the f-electron element interatomic
threshold-distance separating the nonmagnetic state from the magnetic one in
actinides or lanthanides. We have reinvestigated the Hill plot of Ce compounds
using a commercial crystallographic database CRYSTMET, focusing on a
relationship between the Ce-Ce distance and the magnetic ordering temperature,
because a Ce compound with no other magnetic elements scarcely has a magnetic
ordering temperature higher than 20 K. The Hill plot of approximately 730
compounds has revealed that a Ce compound, especially for ferromagnet, showing
the high magnetic-ordering-temperature would require a short Ce-Ce distance
with a suppression of valence instability of Ce ion. Through the study, we had
interest in Ce2AuP3 with the Curie temperature of 31 K. The ferromagnetic
nature has been examined by a doping effect, which suggests a possible increase
of magnetic anisotropy energy.
