1. Crystal structure of Bi₂Te_2.7Se_0.3

2. XRD patterns of powder (a) and single crystal (b) specimens for Bi_1.99Ag_0.01Te₃, Bi₂Te_2.7Se_0.3 and Bi₂Te_2.697Se_0.3I_0.003

3. Two-band model for n- and p-type Bi₂Te₃^{[24,40 -41]} at room temperatureSeebeck coefficient (a, c) and Hall mobility (b, d) along the in-plane direction with respect to the Hall coefficient and Hall carrier concentration; Colorful figures are available on website

4. Two-band model for n- and p-type Bi₂Te_2.7Se_0.3 at room temperature with different mobility ratiosSeebeck coefficient (a, c) and Hall mobility (b, d) along the in-plane direction^{[42⇓⇓⇓⇓⇓⇓-49]} (circles) and random-orientation^{[50⇓⇓-53]} (stars) with respect to the Hall coefficient and Hall carrier concentration, respectively; Varying thicknesses of the lines represents two-band curves simulated with different ratios of mobility for conduction and valence bands; Colorful figures are available on website

5. Room-temperature Seebeck coefficient (a), total thermal conductivity (b), power factor (c), and zT (d) for n- and p-type Bi₂Te_2.7Se_0.3 (along the in-plane direction^{[42⇓⇓⇓⇓⇓⇓-49]} and random-orientation^{[50⇓⇓-53]}) as a function of electrical conductivity, along with the estimation by single-band (dashed lines) and two-band (solid lines) modelsColorful figures are available on website