Recently transition metal based novel alloys have been investigated for the development of high temperature thermoelectric materials. To understand the mechanism and to improve efficiency of such materials several theoretical models have been proposed. Among these the simplest model for analyzing thermoelectric transport of heavily doped semiconductors or semimetals is single parabolic band (SPB) model. This model can guide us to optimize the thermoelectric (power) efficiency (zT=s¬2σT/κ). This model is a good starting point for materials with higher carrier concentration and in region where contribution from minority carriers is negligible. The experimental thermoelectric transport data (ρ,s,k,n) of a sample is used to extract some of the fundamental parameters through SPB model by solving Boltzmann transport equations, assuming that only acoustic phonon scattering constraints the conduction. I shall present the analysis of recent data on RE doped Heusler alloys, using SPB model.