Relativistic electron wave packets carrying angular momentum
  There are important differences between the nonrelativistic and relativistic description of electron beams. The orbital angular momentum quantum number cannot be used to specify the wave functions in the relativistic case. In this Letter we introduce analytic solutions of the Dirac equation in the form of exponential wave packets and we argue that they properly describe relativistic electron beams carrying angular momentum. 
Iwo Bialynicki-Birula and Zofia Bialynicka-Birula
quant-ph