# Feynman Rules from Lagrangian with charge conjugation matrix

I'm dealing with a doubly charged scalar singlet that interacts only with the right-handed muon as follows,

$$\mathcal{L} = \lambda \psi_{R}C\psi_{R} \phi^{++},$$

where $$\lambda$$ is the coupling, $$\psi_{R}$$ is the right-handed muon, $$C$$ is the charge conjugation matrix in some representation and $$\phi^{++}$$ is the doubly charged scalar singlet. My question is, how to extract Feyman's rules from this? More precisely, the vertex.

My first thought was: $$i\lambda \frac{1}{2}(1+\gamma_{5})$$C, but when I think about fermions interacting with a scalar I'm supposing something like $$\mathcal{L} = \lambda \overline{\psi}\psi\phi$$, from where the vertex is $$i\lambda$$. But I don't have an adjoint $$\overline{\psi}$$, and I have no idea how the charge conjugation will get in the vertex expression.