CRYSTAL-FIELD EFFECTS AND F-DERIVED SPECIFIC-HEATS IN HEAVY-FERMION COMPOUNDS

We discuss experimental results of calorimetry on heavy-fermion compounds (HFC) with special regard to the f-derived specific heat ΔC. Attention is given to the extraction of ΔC and the uncertainties implied therein. The discussion includes some Ce-based 4f systems but concentrates on U-based 5f HFC. In four of these (UBe13, UPt3, URu2Si2, U2Zn17) distinct anomalies in ΔC have recently been found in the temperature range between 20 and 100 K which we think are likely to be caused by crystal-field effects thus indicating strong 5f localization.