Quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi2

We report quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi2. The band structure shows several narrow bands with nearly linear energy dispersion and Diraccone-like points at the Fermi level. The quantum oscillation experiments revealed one quasi-twodimensional Fermi pocket and another complex pocket with small cyclotron resonant mass. The in-plane transverse magnetoresistance exhibits a crossover at a critical field B∗ from semiclassical weak-field B dependence to the high-field unsaturated linear magnetoresistance which is attributed to the quantum limit of the Dirac fermions. Our results suggest the existence of quasi 2D Dirac fermions in rare-earth based layered compounds with two-dimensional double-sized Bi square nets, similar to (Ca,Sr)MnBi2, irrespective of magnetic order.