The Bi12.5Sm1.5ReO24.5 phase has been synthesized for the first time. The preparation of Bi12.5Sm1.5ReO24.5 has been carried out by solid-state reaction from Bi2O3,Sm2O3, and Re2O7. The X-ray measurements have showed that Bi12.5Sm1.5ReO24.5 was cubic structure (space group Fm3m). The standard molar enthalpy of formation of Bi12.5Sm1.5ReO24.5 has been determined by solution calorimetry combining the enthalpies of dissolution of Bi12.5Sm1.5ReO24.5 and 6.25Bi(2)O(3) + 0.75Sm(2)O(3) + 0.5Re(2)O(7) mixture in 2 M HCl and literature data. It has been obtained that above-mentioned phase is thermodynamically stable with respect to their decomposition into binary oxides at room temperatures. (C) 2013 Elsevier B.V. All rights reserved.