Crystal structure investigations of VFeSb as-cast and heat treated compounds besides the differential thermal analysis confirmed the polymorphic transformation at 1042 K in these ternary intermetallics. Structure refinements for both low- and high-temperature modifications were performed. The resistivity and thermopower were measured. The charge carrier concentration was calculated from the Hall coefficient measurements for /spl alpha/-VFeSb phase with MgAgAs type structure The figure of merit for this material is /spl sim/0.2/spl times/10/sup -3/ K/sup -1/ at room temperature. Substitutional solid solutions based on the ternary compound were prepared with Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Sr, Ta and Bi. The most efficient dopants for these p- and n-type materials namely Ti, V, Mn and Cu were found.