$\gamma/\gamma$ interfaces fundamentally govern the plastic deformation in lamellar TiAl alloys. The tetragonal nature of the $\gamma$ phase causes $\gamma/\gamma$ twin interfaces to exist in the form of different variants, some of which exhibit coherency stresses or semi-coherent interface structures. While general geometric parameters, such as the lamella spacing and orientation, have been explored extensively in experiments, the isolation of the individual influence of different interfaces in a nano-lamellar microstructure remains a challenge. 

Herein, we atomistically model the range of $\gamma/\gamma$ interface states by using bi-layers of the coherent $\gamma/\gamma_{TT}$ true twin, and the coherent or semi-coherent $\gamma/\gamma_{PT}$ pseudotwin and compare their deformation behavior. We show how the presence of rotational $\gamma/\gamma$ interfaces with inherent misfit is responsible for localized and early plasticity, that can substantially lower the strength of a lamellar microstructure. This finding is consistent with experimental studies of microplastic behaviour in TiAl and thus make a point that interface type should also be used as a criterion for alloy microstructure design in the future.