Polycrystalline bulk of higher manganese silicide (HMS) was prepared by heating a compact body of Mn powder in a Na-Si melt at 800 degrees C for 12 h. The density of the bulk sample was 75% of the theoretical one. The sample showed the highest non-dimensional figure of merit, ZT, of 0.31 at 525 degrees C. Inhomogeneous distributions of Mn and Fe were observed in the Fe-containing bulk samples prepared from the compact bodies of the mixtures of Mn and Fe powders. The relative densities of samples containing 10 and 20 at.% Fe were 80 and 84% of the theoretical density of HMS, respectively. The maximum ZT values of the samples were 0.31 at 525 degrees C for the 10 at.% Fe-containing sample and 0.06 at 475 degrees C for the 20 at.% one. (C) 2011 Elsevier B. V. All rights reserved.