Pressure- and field-dependent behavior ofYbCu4Au

Temperature- and pressure-dependent measurements of the electrical resistivity ρ(T,p) of the ternary compound ${\mathrm{YbCu}}_4$Au have been performed. These investigations yield an increase of the antiferromagnetic transition temperature ${\mathit{T}}_{\mathit{N}}$ from 0.6 K at ambient pressure up to more than 2 K at 50 kbar. The bulk modulus has been determined (${\mathit{B}}_0$≊1.4 Mbar) at room temperature which together with ∂${\mathit{T}}_{\mathit{N}}$/∂p≊0.044 K/kbar derived from ρ(T,p) allows an estimation of the Grüneisen constant Ω(${\mathit{T}}_{\mathit{N}}$)≊60. A study of the field-dependent behavior of the specific heat justifies an antiferromagnetic ground state. In the scope of an empirical model, the Kondo temperature ${\mathit{T}}_{\mathit{K}}$ of ${\mathrm{YbCu}}_4$Au was obtained to be 1.65 K, which is significantly smaller than the energy of the first excited crystal-field level above the ground-state doublet.