  We report on van der Waals epitaxial growth, materials characterization and
magnetotransport experiments in crystalline nanosheets of Bismuth
Telluro-Sulfide (BTS). Highly layered, good-quality crystalline nanosheets of
BTS are obtained on SiO$_2$ and muscovite mica. Weak-antilocalization (WAL),
electron-electron interaction-driven insulating ground state and universal
conductance fluctuations are observed in magnetotransport experiments on BTS
devices. Temperature, thickness and magnetic field dependence of the transport
data indicate the presence of two-dimensional surface states along with bulk
conduction, in agreement with theoretical models. An extended-WAL model is
proposed and utilized in conjunction with a two-channel conduction model to
analyze the data, revealing a surface component and evidence of multiple
conducting channels. A facile growth method and detailed magnetotransport
results indicating BTS as an alternative topological insulator material system
are presented.
