Magnetotransport study of Dirac fermions in YbMnBi2 and CaMnBi2*

It is well known that AMnBi$_{2}$ (A $=$ alkaline earth) with two dimensional (2D) bismuth layer host quasi-2D Dirac states similar to graphene and topological insulators. The Dirac state is significantly affected by the alkaline earth in the block layer. Angle-resolved photoemission spectroscopy (ARPES) indicates that YbMnBi$_{2}$ could be the first Weyl semimetal with time-reversal symmetry breaking, whereas the anisotropic Dirac state in SrMnBi$_{2}$ can host a valley-polarized interlayer current through magnetic valley control. Here, we study in-plane magnetotransport in YbMnBi$_{2}$, and interlayer magnetotransport in CaMnBi$_{2}$. The angular-dependent magnetoresistance, nonzero Berry phase, and small cyclotron mass confirm the presence of Dirac fermion and quasi-2D fermi surface in YbMnBi$_{2}$. The interlayer electronic transport in CaMnBi$_{2}$ suggest valley polarized conduction and a Dirac state on the side wall of the warped cylindrical Fermi surface of CaMnBi$_{2}$.