Specific heat of Ca0.33Na0.67Fe2As2

The specific heat of single crystal hole-doped Ca0.33Na0.67Fe2As2, T c onset =33.7 K, was measured from 0.4 to 40 K. The discontinuity in the specific heat at Tc, ΔC, divided by Tc is 105±5 mJ/mol K2, consistent with values found previously for hole-doped Ba0.6K0.4Fe2As2 and somewhat above the general trend for ΔC/Tc vs Tc for the iron based superconductors established by Bud׳ko, Ni and Canfield. The usefulness of measured values of ΔC/Tc as an important metric for the quality of samples is discussed.