Fig. 4: Electrical transport characterizations.

a–c Electrical conductivities of three materials as a function of temperature from 2 to 400 K. Inset, plots of ln(σ) versus T−1/4 over the temperature region of 100–250 K. d UPS data for the valence band region of three samples acquired at 300 K, and the Fermi edge was shown by the pink dotted line. Source data are provided as a Source Data file.