Giant magnetoresistance in layered manganese pnictide CaMnBi2

We report the physical properties of a layered transition metal pnictide, CaMnBi2, which has a crystal structure similar to that of the superconducting iron pnictides. This compound is a bad metal with a long-range antiferromagnetic order at TN = 270 K. The linear temperature dependence of magnetic susceptibility above TN suggests that strong antiferromagnetic correlations exist in the paramagnetic state. A linear magnetic field dependence of the magnetoresistance implies the existence of the linear energy dispersion, which may result in the giant in-plane magnetoresistance (about 105% in 10 T at 2.5 K for H∥c). The results of de Haas-van Alphen effect are consistent with the presence of Dirac fermions.