  One of the most important properties of very recently reported FeSe based
superconductors is the robustness of their superconductivity under applied
magnetic field. The synthesis and control of superconductivity in FeSe based
compounds is rather a difficult task. Synthesis and physical property
characterization for optimized superconductivity of FeSe1/2Te1/2 at 13 K is
reported here. The compound crystallized in a tetragonal structure with lattice
parameters a = 3.8008(10) and c = 6.0187 (15) A. Magnetization measurements
indicated bulk superconductivity with lower critical field (Hc1) of around 180
Oe. By applying Ginzburg Landau (GL) theory, the Hc2(0) value is estimated to
be = 1840 kOe for the 90% of resistive transition. A heat capacity measurement
revealed bulk superconductivity by a hump at Tc near 13 K, and an expected
decrease was observed under an applied magnetic field.
