A Kleppa type microcalorimeter was designed and constructed for the application to measure the thermal change in a reaction tube at T > 1300 K. The details of new calorimeter are described. In order to verify the performance of the new calorimeter, the standard enthalpies of formation for NiSi and Ni3Al were measured by direct synthesis in the calorimeter at T = 1323 K. The enthalpies of formation obtained were -(79.3 +/- 1.8) and -(189.3 +/- 6.3) kJ(.)mol(-1) for NiSi and Ni3Al, respectively. A comparison of results in the present work with available reported values has been made. (C) 2003 Elsevier Ltd. All rights reserved.