BaMn$_{2}$Sb$_{2}$: A New Semiconducting Ferromagnet*

We have grown high-quality single crystals of BaMn$_{2}$Sb$_{2}$, which possesses the ThCr$_{2}$Si$_{2}$ structure as determined by X-ray powder diffraction technique. Magnetization measurements indicate that BaMn$_{2}$Fe$_{2}$ is ferromagnetic below $T_{C}$ = 580K. On the other hand, the temperature dependence of electrical resistivity shows semiconducting behavior, which can be described by thermally-activated resistivity formula with thermal activation energy about 0.25 eV . While the Hall coefficient has positive sign between 2 and 300 K, the Seebeck Coefficient undergoes sign change from positive at high temperatures to negative at low temperatures, reaching -260 $\mu $V/K at 70 K. The implication will be discussed.