UC Irvine

We report resistivity measurements on the cubic heavy-fermion compound YbBiPt at ambient and hydrostatic pressures to ≅6 kbar and in magnetic fields to 1 T. Resistivity anisotropy sets in below the phase-transition temperature Tc=0.4 K. We interpret a rise of resistivity below 0.4 K as due to partial gapping of the Fermi surface with the weak coupling energy gap of Δ0kBTc=1.65±0.15. Effects of hydrostatic pressure and magnetic field on the phase transition and heat capacity data are consistent with a spin density wave formation in a very heavy electron band at T=0.4 K.