Thermal properties of heavy-fermionCeRu2Si2

We present measurements of the coefficients of linear thermal expansion of single-crystalline samples of the tetragonal heavy-fermion compound ${\mathrm{CeRu}}_2$ ${\mathrm{Si}}_2$, and its nonmagnetic analog ${\mathrm{LaRu}}_2$ ${\mathrm{Si}}_2$, in the temperature range 1.5–270 K. The electronic part of the thermal expansion of ${\mathrm{CeRu}}_2$ ${\mathrm{Si}}_2$ yields two distinct anomalies: (1) a huge positive contribution, caused by the (antiferro)magnetic interactions between the quasiparticles, centered at 9 K, and (2) a negative crystal-field contribution centered at 120 K. The data are compared with existing specific-heat data (T<100 K). An analysis in terms of Grüneisen parameters yields the very large value of ${\Gamma }_{\mathrm{hf}=190\mathrm{}}$ for the low-temperature contribution and a value ${\Gamma }_{\mathrm{cf}=\mathrm{-}5.3}$ for the crystal-field contribution. A quantitative analysis using a simple single resonance-level model yields a Kondo-type temperature of 19 K. An analysis of the crystal-field contribution yields a first excited level at 288 K. We also discuss low-temperature scaling behavior by comparing new magnetostriction measurements, that cover the metamagnetic behavior, with magnetization data.