Fig. 1. Structure, plasticity, and thermoelectric properties of α-Mg₃Bi₂ single crystals.

a Crystal structure of α-Mg₃Bi₂, in which Mg atoms occupy two distinct lattice sites (Mg1 and Mg2). The atom arrangement of α-Mg₃Bi₂ comprises periodic small-sized Mg²⁺ interlayers and covalent bonded Mg₂Bi₂²⁻ networks. b An as-grown n-type α-Mg₃Bi₂ crystal, the letters “SUSTECH” and a flexible chain deformed by crystal slabs. c Uniaxial compression experiments. α-Mg₃Bi₂ crystals sustained >90% compression strain. d Deformability factor Ξ of α-Mg₃Bi₂ and several other materials (listed in Supplementary Table 1)^30,32,34,35. e Room-temperature power factors for inorganic plastic inorganic semiconductors (listed in Supplementary Table 2)^{6,20–29,31,39}. The electrical transport performance of α-Mg₃Bi₂ was better than that of liquid-like plastic inorganic semiconductors and van der Waals semiconductors. f Normalized power density (P_max/AΔT²) of out-of-plane flexible thermoelectric devices (listed in Supplementary Table 3)^6,9,40–50, including α-Mg₃Bi₂ based^40,41, liquid-like material-based^6,50, Bi₂Te₃-based^42–46, and organic material-based^9,47–49 devices. Our data are marked by red stars.