  Bulk superconductivity has been discovered in Tl_{0.6}Bi_{2}Te_{3}, which is
derived from the topological insulator Bi2Te3. The superconducting volume
fraction of up to 95% (determined from specific heat) with Tc of 2.28 K was
observed. The carriers are p-type with the density of ~1.8 x 10^{20} cm^{-3}.
Resistive transitions under magnetic fields point to an unconventional
temperature dependence of the upper critical field B_{c2}. The crystal
structure appears to be unchanged from Bi2Te3 with a shorter c-lattice
parameter, which, together with the Rietveld analysis, suggests that Tl ions
are incorporated but not intercalated. This material is an interesting
candidate of a topological superconductor which may be realized by the strong
spin-orbit coupling inherent to topological insulators.
