β-K2Bi8Se13 and its solid solutions have been found to be interesting for thermoelectric investigations mainly due to their low thermal conductivity and highly anisotropic electrical properties. Solid solution series of the type K2Bi8-xSb xSe13, K2-xRbxBi8Se 13 as well as K2Bi8Se13-xS x has been studied. Interestingly, K2Bi 8-xSbxSe13 presents both n- and p-type of character depending on the Sb concentration in the lattice. In this work, the n-to-p transition with Sb concentration is presented. The Seebeck coefficient is discussed as a function of x and the transition at room temperature appears at the stoichiometric region of x∼6. The transition temperature for the members of the series increases with Sb incorporation in the lattice and this can be attributed to the band gap increase.