  We have synthesized single crystals of Dirac semimetal candidates AZnBi2 with
A=Ba and Sr. In contrast to A=Sr, the Ba material displays a novel local Zn
vacancy ordering, which makes the observation of quantum oscillations in
out-of-plane magnetic fields possible. As a new Dirac semimetal candidate,
BaZnBi2 exhibits small cyclotron electron mass, high quantum mobility, and
non-trivial Berry phases. Three Dirac dispersions are observed by ARPES and
identified by first- principles band-structure calculations. Compared to
AMn(Bi/Sb)2 systems which host Mn magnetic moments, BaZnBi2 acts as
non-magnetic analogue to investigate the intrinsic properties of Dirac fermions
in this structure family.
