Specific heat studies of PrCoAl4 single crystal

We have studied the heat capacity of a single crystal PrCoAl4. The data indicate that Pr3+ in this compound has a non-magnetic singlet ground state. The compound becomes antiferromagnetically ordered below the Neel temperature of 17 K. The magnetocrystalline anisotropy in PrCoAl4 is relatively strong. Up to 300 K, the entropy contained in the specific heat is 15.2 J/Kmol, which is only 83% of 18.3 J/Kmol expected for the 2J+1-fold degeneracy of the ground multiplet of the Pr3+ ion.