A thermoelectric material of the p-type having the stoichiometric formula Zn4Sb3, wherein part of the Zn atoms optionally being substituted by one or more elements selected from the group comprising Sn, Mg, Pb and the transition metals in a total amount of 20 mol % or less in relation to the Zn atoms is provided by a process involving zone-melting of a an arrangement comprising an interphase between a “stoichiometric” material having the desired composition and a “non-stoichiometric” material having a composition deviating from the desired composition. The thermoelectric materials obtained exhibit excellent figure of merits.