both high electron mobility and enhanced Seebeck coefficient due to energy-dependent carrier scattering as well as strengthened phonon blocking are realized in the composites, which lead to ~38% increase of power factor (PF) besides a large reduction (40% at 300K) of lattice thermal conductivity in the SnxBi2Te2.7Se0.3 based composites as Sn content f ¼ 0.2 wt%. Conse-quently, both high maximum ZT (ZTmax ¼ 1.11 at ~370 K) and large average ZT (ZTave ¼ 1.03 at operative temperature range of 300K–500K) are achieved.