  We investigated the physical properties of $TlFe_{2-x}Se_2$ single crystals.
The resistivity of $TlFe_{2-x}Se_2$ shows typical semiconductor behavior with
an activation energy of 25 meV. DC susceptibility indicates an
antiferromagnetic transition at about 450 K. Reentrant spin-glass (RSG)
behavior was found at about 130 K through DC and AC magnetic measurements. The
RSG behavior suggests the existence of a strong competition between
ferromagnetic (FM) and antiferromagnetic (AFM) interactions due to Fe
deficiencies. Strong electron-electron correlation may exist in this material
and it is possibly a candidate of parent compound for high $T_c$
superconductors.
