The temperature dependence of electrical resistivity (ρ) and Seebeck co-efficient (S) have been measured which show significant change in their behaviour while substituting Sn for Al. A sharp decrease in the ρ, and substantial enhancement in S can be explained on the basis of the electronic band structure where the Fermi level shifts slightly from the center of pseudogap. Further, the values of thermoelectric power factor are increase for lower doping levels of Sn which are quite comparable to that of conventional thermoelectric material and Si substituted Heusler alloys. © 2012 American Institute of Physics.