  Previous band structure calculations predicted Ag3AuSe2 to be a semiconductor
with a band gap of approximately 1 eV. Here, we report single crystal growth of
Ag3AuSe2 and its transport and optical properties. Single crystals of Ag3AuSe2
were synthesized by slow-cooling from the melt, and grain sizes were confirmed
to be greater than 2 mm using electron backscatter diffraction. Optical and
transport measurements reveal that Ag3AuSe2 is a highly resistive semiconductor
with a band gap of and activation energy around 0.3 eV. Our first-principles
calculations show that the experimentally-determined band gap lies between the
predicted band gaps from GGA and hybrid functionals. We predict band inversion
to be possible by applying tensile strain. The sensitivity of the gap to Ag/Au
ordering, chemical substitution, and heat treatment merit further
investigation.
