  Using the non-equilibrium Green's function technique, we calculate spin-orbit
torques in a Mn$_2$Au/heavy-metal bilayer, where the heavy metal (HM) is W or
Pt. Spin-orbit coupling (SOC) in the bulk of Mn$_2$Au generates strong
fieldlike torquance, which is parallel on the two sublattices and scales
linearly with the conductivity, and a weaker dampinglike torquance that is
antiparallel on the two sublattices. Interfaces with W or Pt generate parallel
dampinglike torques of opposite signs that are similar in magnitude to those in
ferromagnetic bilayers and similarly insensitive to disorder. The dampinglike
torque efficiency depends strongly on the termination of the interface and on
the presence of spin-orbit coupling in Mn$_2$Au, suggesting that the
dampinglike torque is not due solely to the spin-Hall effect in the HM layer.
Interfaces also induce antiparallel fieldlike and dampinglike torques that can
penetrate deep into Mn$_2$Au.
