  The results of dc magnetization, electrical and magnetoresistance and heat
capacity measurements (2-300 K) on Tb7Rh3, crystallizing in Th7Fe3-type
hexagonal structure, are reported. In this compound, magnetic ordering sets in
around 90 K with additional transitions at low temperatures and the temperature
coefficient of resistivity (R), dR/dT, is negative over a wide temperature
range in the paramagnetic state. The present magnetization results reveal that
this compound is apparently characterized by rich features in the
magnetic-field-temperature phase diagram. A point of major emphasis is that the
sign of dR/dT in the paramagnetic state can be gradually changed by the
application of magnetic field. As a result, the magnitude of the
magnetoresistance (MR) is rather large even in the vicinity of room temperature
(far above magnetic ordering temperature), in addition to giant MR behavior in
the magnetically ordered state. Viewed together With similar behavior for other
heavy rare-earth members of this series, this class of compounds can be
classified as Paramagnetic Giant Magnetoresistance Systems. A new theoretical
approach is warranted to understand this phenomenon.
