We obtained via solid state synthesis needle-shaped crystals of In5Se5Br crystallizing in the space group Pmn2(1) and containing indium simultaneously in three different oxidation states: In+, formal In2+ and In3+. Bulk sample of In5Se5Br shows n-type conductivity and linear increase of Seebeck voltage with the temperature difference increase. Seebeck voltage of approx. 720 mV is recorded at a temperature difference of 80 K, corresponding to a Seebeck coefficient -8900 mu V/K. A voltage increase up to 250 mV is recorded within 10 min upon application of a 27 K temperature difference between the contacts. On-off switching of the heating source unveils repeatable results. Linear I-U behavior with a resistivity of 2.32 x 10(11) Omega is observable for individual needles of In5Se5Br. In bulk In5Se5Br the resistivity oscillates between 2.6 M Omega and 23 M Omega. DTA and HT-powder XRD data show incongruent melting to InBr, InSe and In2Se3 at 805 K. The ternary compound expands 1.02% along [0 1 0] showing a coefficient of thermal expansion alpha(b) = 2.3(4) x 10(-5) K-1. Lower expansions of 0.6% and 0.16% along a and c axes corresponding to mean coefficients of thermal expansion of (alpha(a)) over bar = 1.3(1) x 10(-5) K-1, (alpha(c)) over bar = 4.4(5) x 10(-6) K-1 are observed. Thin layer growing of In5Se5Br on glass substrate with targeted doping/substitutions can improve the sample conductivity, increase the Seebeck coefficient and lower the thermal conductivity making In5Se5Br a good alternative material for industrial thermoelectric applications. (C) 2014 Elsevier Ltd. All rights reserved.