Temperature-dependent electrical conductivity of (A), temperature-dependent Hall mobility of (B), composition-dependent temperature exponent of (C), and relationship between Hall carrier concentration, nH, and Hall mobility for (D) Mg3.2Sb1.5Bi0.49Te0.01 and Mg3.1A0.1Sb1.5Bi0.49Te0.01 (A = Fe, Co, Hf, and Ta). Data from ref. 33 in panel A and Nb data in panel D from ref. 35.