The effects of doping and pressure on the U3Sb4Pt3 system have been studied. Substitution of either trivalent yttrium or lutetium for uranium causes significant changes in the temperature dependences of the electrical resistance and of the magnitude of the linear coefficient of the specific heat γ. However, substitution of tetravalent thorium causes little change in γ, even though it affects the electrical resistance in a manner similar to that seen in the cases of lutetium and yttrium. Finally, application of hydrostatic pressures up to 16.5 kbar causes no significant change in the electronic gap deduced from the electrical resistance. © 1992.

The compound YbBiPt exhibits an extremely large low-temperature C/T (γ∼8 J K-2 mol-1/Yb) which, if due solely to a renormalized effective mass, would make this material the heaviest correlated electron system known to date. In the Kondo model, the very large γ corresponds to a small characteristic energy scale that is expected to be pressure dependent. We have studied the effect of chemical pressure on YbBiPt single crystals by heat-capacity measurements on Y and Lu-doped samples. We have also made preliminary low-temperature measurements under hydrostatic pressure of the heat capacity (300 mK≤T≤2 K, up to 8 kbar) and resistance (30 mK≤T≤1 K, at 16 kbar).

We have discovered a new family of rare earth compounds that we identify as R2-xPt4Ga8+y. Single crystals of this family have been grown for RLa, Ce, Pr, Nd, Sm, Gd, Er, Yb and Y. Many members (cerium, praseodymium, neodymium, samarium and erbium) show large anisotropies in their magnetic susceptibility; further, electrical resistance, magnetic susceptibility and specific heat measurements on the cerium member indicate that it is very possibly a heavy-electron compound with an electronic specific heat γ ≈ 1 J K-2 mol-1. Additionally, other members of the family have a magnetic transition at low temperatures. The electrical resistance, magnetic susceptibility and specific heat in fields will be presented for the praseodymium-based compound in which there is a field-induced transition. © 1992.