High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt

YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below $T^{\rm{*}}=0.7$~K, fragile antiferromagnetic order below $T_{\rm{N}}=0.4$~K, a Kondo temperature of $T_{\rm{K}} \approx1$~K, and crystalline-electric-field splitting (CEF) on the order of $E/k_{\rm{B}}=1\,\rm{-}\,10$~K. Its lattice is face-centered cubic at ambient temperature, but certain data, particularly those from studies aimed at determining the CEF level scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-energy x-ray diffraction experiments which show that, within our experimental resolution of $\approx6\,\rm{-}\,10\times10^{-5}$~\AA, no structural phase transition occurs between $1.5 $ and $50$~K. Despite this result, we demonstrate that the compound's thermal expansion may be modeled using CEF level schemes appropriate for Yb$^{3+}$ residing on a site with either cubic or less than cubic point symmetry.\\Work at the Ames Laboratory was supported by the US DOE, BES, DMSE, under Contract No. DE-AC02-07CH11358. Work at Occidental College was supported by the NSF under DMR-1408598. This research used resources at the Advanced Photon Source a US DOE, Office of Science, User Facility.