Explorations
of benzene-based organic superconductors and bismuth-based
functional materials are today’s hottest topics in chemistry,
physics, and materials science. Here, we show that by doping potassium
into an organobismuth molecule, tri-p-tolylbismuthine,
which is composed of one bismuth atom and three methylphenyl groups,
all synthesized samples exhibit type-II superconductivity at 3.6 K
at ambient pressure and one sample also shows superconductivity at
5.3 K. The common 3.6 K superconducting phase is identified to have
a triclinic P1 structure, with a mole ratio of 3:1 between potassium
and tri-p-tolylbismuthine. The calculated electronic
structure indicates that superconductivity is produced by transferring
an electron from K 4s to the C 2p orbital, which results in both red
and blue shifts of the Raman spectra. Our study enriches the physical
functionality of organobismuth compounds and illustrates a new route
for the search of organic superconductors.