Can CP-violation arise due to interference between two tree-level diagrams in a QFT?

In Leptogenesis, CP-asymetry arises due to the interference of the tree-level amplitude $N\rightarrow l_\alpha\phi$ (where $N$ is heavy sterile neutrino, $l_\alpha$ is a lepton flavour, and $\phi$ is the Higgs) with the higher order amplitudes (say, one-loop amplitude). This was a decay. Let us consider an scattering so that there may me more than one diagrams at the tree level. For a given scattering $A+B\rightarrow C+D$, there may be two tree-level diagrams. Similarly for the process $\bar{A}+\bar{B}\rightarrow \bar{C}+\bar{D}$ where will be two again. Can we have CP-asymetry due to the interference between two different tree-level scattering amplitudes? I believe the question makes sense. If not I shall try to clarify it further.