Dirac semimetal and topological phase transitions in A3Bi (A=Na, K, Rb)
  The three-dimensional (3D) Dirac point, where two Weyl points overlap in momentum space, is usually unstable and hard to realize. Here we show, based on the first-principles calculations and effective model analysis, that crystalline $A_3$Bi ($A$=Na, K, Rb) are Dirac semimetals with bulk 3D Dirac points protected by crystal symmetry. They possess non-trivial Fermi arcs on the surfaces, and can be driven into various topologically distinct phases by explicit breaking of symmetries. Giant diamagnetism, linear quantum magnetoresistance, and quantum spin-Hall effect will be expected for such compounds. 
Zhijun Wang, Yan Sun, Xingqiu Chen, Cesare Franchini, Gang Xu,   Hongming Weng, Xi Dai, Zhong Fang
cond-mat.mtrl-sci