H. Fujii et al., UNUSUAL MAGNETIC, TRANSPORT AND THERMODYNAMICAL PROPERTIES OF THE URANIUM TERNARIES UNISN, UPDIN AND UNIGA, Physica. B, Condensed matter, 192(3), 1993, pp. 219-227
We present our recent results of systematic experimental work on magne
tic, transport and thermodynamical properties of the equiatomic ternar
ies UNiSn, UPdIn and UNiGa. UNiSn with cubic MgAgAs-type structure exh
ibits a semi-conductor-to-metal transition associated with a type-I an
tiferromagnetic ordering. Both UPdIn and UNiGa crystallize in the hexa
gonal ZrNiAl-type structure. UPdIn is the first example of a two-dimen
sional heavy-fermion system accompanied by a pseudogap formation along
the c-axis due to the development of the c-axis modulated magnetic st
ructure. UNiGa exhibits a giant magnetoresistance being as large as DE
LTArho/rho congruent-to 90% at T = 1.5 K for the current parallel to t
he c-axis, which is a result of the antiferromagnetic-to-ferromagnetic
transition occurring at B=0.7 T. All of these unusual physical proper
ties can be a consequence of the change in the hybridization of the hi
ghly correlated 5f-electrons with s, p or d electron states by the dev
elopment of magnetic ordering or the magnetic order-order transition.