Heavy-Fermion Properties of Yb₂Pd₂SnH≈₂

Abstract

A hydride of Yb₂Pd₂Sn could be synthesized with approximately 2 H atoms per f.u. The hydrogenation leads to a volume expansion while preserving the tetragonal symmetry (P4/mbm). The lattice reaction is strongly anisotropic, and the 5% expansion in c is partly compensated by the 0.5% compression in a. The hydride is paramagnetic at least down to 0.5 K. Yb remains at or very close to the 3+ (4f¹³) state, as in Yb₂Pd₂Sn. Specific heat C/T vs. T shows an upturn existing already in Yb₂Pd₂Sn, but it is much more pronounced in the hydride (1.8 J/mol f.u. K² for T → 0, i.e., more than twice higher than in its precursor). This is interpreted as lowering the Kondo temperature due to H bonding.