“…The HH composites have the form XYZ, where X belongs to the first column of the main group, Y represents a rare earth element, transition metal or noble metal (X and Y=Zr, Cr, Na, K, Li, Zn, Cd, Mn, Ni, Ir, Co, and Fe), and Z denotes the sp-valent elements (Z=Al, Sn, Sb, P, In, Si, Ge, As, and Ga) [6][7][8]. HH has attracted extensive interest, not only because they use cheap, abundant, lightweight, and environment-friendly elements, but also because they combine high 'Seebeck -coefficients' with electrically moderately low resistivities, resulting in inherently high-power factors [9][10][11][12]. At high temperatures, many electrons become thermally excited from the 'valence band' to the 'conduction band', leaving behind them an equal number of holes.…”