NOVELTY - Thermoelectric material, comprises a half-Heusler compound comprising a composition (I) or (II) containing titanium or zirconium, nickel and tin.    USE - The thermoelectric material is useful in thermoelectric devices, which are useful in solar thermoelectric generator, sea water temperature difference thermoelectric power generator, fossil fuel thermoelectric power generator, regenerative power generator of factory exhaust heat and automotive exhaust heat, photon-detection device, laser diode, field effect transistor, photo-multiplier, cell of spectrum photometer, column of chromatography, constant-temperature unit, air conditioning and heating equipment, refrigerator and power source of clocks.    ADVANTAGE - The thermoelectric material reduces the thermal conductivity of the titanium, nickel and tin based compound or zirconium, nickel and tin based compound without the use of an expensive heavy element, which includes zirconium or hafnium, thus allows the dimensionless figure of merit to be improved.    DETAILED DESCRIPTION - Thermoelectric material, comprises a half-Heusler compound comprising a composition containing titanium or zirconium, nickel and tin of formula ((Ti(1-a)A1a)(1+x)(Ni(1-b)B1b)(1+y)(Sn(1-c)C1c)) (I) (where amounts of Zr substitution and Hf substitution at Ti sites of the half-Heusler compound are less than 1 at %, respectively) or ((Zr(1-a)A2a)(1+x)(Ni(1-b)B2b)(1+y1)(Sn(1-c)C2c)) (II) (where an amount of Hf substitution at Zr sites of the half-Heusler compound is less than 1 at %).    a, h, c = 0-0.1;    x = -0.1 to 0.2;    y, y1 = greater than 0 to 0.2;    A1, A2 = at least one element, which is group IIIa element, group IVa element (excluding Ti), group Va element or rare earth element;    B1, B2 = at least one element, which is group VIIIa element (excluding Ni) or group Ib element; and    C1, C2 = at least one element, which is group IIIb element, group IVb element (excluding Sn) or group Vb element.    An INDEPENDENT CLAIM is also included for manufacturing a thermoelectric material, comprising a rapid cooling step in which a molten metal obtained by melting a raw material weighed so as to become the half-Heusler compound or obtained by remelting an ingot produced by melting a raw material weighed so as to become the half-Heusler compound and then by casting the molten metal, which is rapidly solidified.