While the Heusler-type Fe(2)VAI compound exhibits a semiconductor-like behaviour in electrical resistivity, doping of quaternary elements causes a sharp decrease in the low-temperature resistivity rho and a large enhancement in the Seebeck coefficient S. Substantial enhancement in S can be explained on the basis of the electronic structure where the Fermi level shifts slightly from the center of a pseudogap either up- or downward depending on doping. In particular, a slight substitution of Si for Al leads to a large power factor (P = S-2/p) of 5.5 x 10(-3) W/mK(2) at around room temperature.