Specific heat of a Kondo superconductor: (La, Ce) Al₂

The specific heat of LaAl2 and (La1-xCex)Al2 (x ⩽ 0.0064) has been measured between 0.3 and 5 K, both in the superconducting and in the normal state. For all samples the same values for the Debye temperature as well as for the electronic specific heat coefficient have been determined. LaAl2 shows an excellent BCS behavior. A remarkable excess specific heat at low temperatures due to the Kondo effect has been observed for all superconducting as well as for the normal conducting (La1-xCex) Al2 alloys. The specific heat jump ΔC at Tc depressed rapidly with increasing Ce concentration, allows the Kondo temperature TK ≅ 1 K to be determined. ΔC vanishes at finite temperatures