Heat flux calorimetry was used to measure the heat capacity of NaF between 630K and 1100K. The results agreed well with previous measurements known from the literature. Similar experiments were performed on NaLaF 4 . This compound was synthesized from NaF and LaF 3 and analyzed by X-ray diffraction. The heat capacity of NaLaF 4 was determined for two temperature ranges: from 4K to 400K, for which adiabatic calorimetry, and from 623K to 1213K for which differential scanning heat flux calorimetry was used. The two heat capacity series fit smoothly; the resulting C p,m function was used in a reassessment of the binary system (NaF+LaF 3 ).