  Using first-principles calculations, we show that Fe2VAl is an indirect band
gap semiconductor. Our calculations reveal that its, sometimes assigned,
semimetallic character is not an intrinsic property but originates from the
antisite defects and site disorder, which introduce localized ingap and
resonant states changing the electronic properties close to band gap. These
states negatively affect the thermopower S and power factor PF=S^2\sigma,
decreasing the good thermoelectric performance of intrinsic Fe2VAl.
