A thermoelectric half-Heusler material comprising niobium (Nb), iron (Fe) and antimony (Sb) wherein the material comprises grains having a mean grain size less than one micron. A method of making a nanocomposite half-Heusler thermoelectric material includes melting constituent elements of the thermoelectric material to form an alloy of the thermoelectric material. comminuting (e.g .• ball milling) the alloy of the thermoelectric material into nanometer scale mean size particles. and consolidating the nanometer size particles to form the half-Heusler thermoelectric material comprising niobium (Nb), iron (Fe) and antimony (Sb) and having grains with a mean grain size less than one micron.