. Crystal structures for the different phases of AgBiSe₂ (a) and phase diagram of Ag₂Se-Bi₂Se₃ system (b)^[57]

. Powder XRD patterns for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.4≤x≤0.62)

. Locally enlarged XRD patterns (a) and composition dependent lattice parameters (b) for the samples with 0.48≤x≤0.56

. SEM images for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.48≤x≤0.56) (a, c-g) and its corresponding EDS mapping for the samples with x=0.48 (b) and 0.58 (h)

. Composition dependent Hall carrier concentration (a) and normalized optical absorption versus photon energy (b) at room temperature for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.5≤x≤0.56)

. Temperature dependent Hall coefficient (R_H) and mobility (µ_H) (a), deformation potential coefficient (E_def) and density of states effective mass (m^*) (b), Hall carrier concentration dependent Hall mobility (c) and Seebeck coefficient (d) at different temperatures for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.5≤x≤0.56), with a comparison to available literature results^[52,64-65].
The experimental results here agree well with the model prediction based on a SPB approximation with a dominant scattering by acoustic phonons

. Temperature dependent Seebeck coefficient (a), electrical resistivity (b), total thermal conductivity (c) and lattice thermal conductivity (d) for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.5≤x≤0.56), with a comparison to available literature results^[63,64]

. Temperature dependent ZT for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.5≤x≤0.56) (a) and Hall carrier concentration dependentZT at different temperatures (b) with a comparison to model prediction and literature results^[52,63-65]

Table 1. Measured sound velocities and the estimated physical parameters for (Ag₂Se)_1-x(Bi₂Se₃)_x(0.5≤x≤0.56)