The structure of Ba-5(MnO4)(3)Cl is refined by the Rietveld method (space group P6(3)/m). The heat capacities of Ba-5(MnO4)(3)Cl apatite were measured by precision adiabatic vacuum calorimetry over the temperature range from T = (6-348) K. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity Cp degrees(T), enthalpy H degrees(T) - H degrees(0), entropy S degrees(T) - S degrees(0) and Gibbs function G degrees(T) - G degrees(0), for the range from (0 to 350) K. (C) 2018 Elsevier Ltd.