Non-magnetic-doublet ground state in PrInCu2; Enhancement of the specific-heat coefficient at low temperatures

Specific heat, C, thermoelectric power, S, and magnetic susceptibility, χ, of a cubic Heusler compound PrInCu2 have been carefully examined. The C/T shows an enhancement with decreasing T and reaches 1.1J/molK2 at 0.5K, while the S/T does not show any enhancement at temperatures below 1K. These observations suggest that the conduction electrons at EF do not correlate with the 4f electrons of Pr atoms and that the enhancement of C/T is not due to the Kondo effect. To explain the enhancement of the C/T at low temperatures, a model that the non-magnetic doublet of PrInCu2 is lifted by quadrupole fluctuations was proposed. From the analysis of overall features of C(T) and χ(T), the energy scheme of 4f electrons was derived