Thermoelectric properties of Heusler-type (Fe1-xCox)2TiAl alloys

We report on the temperature dependence of the electrical resistivity and the Seebeck coefficient for the Heusler-type (Fe1-xCox)(2)TiAl alloys with compositions 0.25 <= x <= 0.70. A small deviation from stoichiometry (x=0.50) causes a decrease in the electrical resistivity and an enhancement in the Seebeck coefficient with positive and negative sign for x<0.45 and x >= 0.45, respectively. This compositional variation of the Seebeck coefficient is in line with a pseudogap scenario where the off-stoichiometry causes a rigid-band-like shift of the Fermi level from the central region in the pseudogap. The measured Seebeck coefficient is found to be lower than that evaluated from the theoretical density of states, which may be attributed to an atomic disorder between Fe and Co.