Abstract
We present the specific-heat study of the electronic properties of NpIrSn and NpNiSn. NpIrSn orders antiferromagnetically below TN = 38K and undergoes a further magnetic phase transition at T1 = 23.5K.
The gamma-coefficient of the electronic specific heat is only moderately enhanced to 75mJ mol-1 K-2. NpNiSn orders antiferromagnetically below TN = 35.5K.
In both compounds the antiferromagnetic order is not affected by magnetic fields up to 14 T.