  We define Mellin amplitudes for the fermion-scalar four point function and
the fermion four point function. The Mellin amplitude thus defined has multiple
components each associated with a tensor structure. In the case of three
spacetime dimensions, we explicitly show that each component factorizes on
dynamical poles onto components of the Mellin amplitudes for the corresponding
three point functions. The novelty here is that for a given exchanged primary,
each component of the Mellin amplitude may in general have more than one series
of poles. We present a few examples of Mellin amplitudes for tree-level Witten
diagrams and tree-level conformal Feynman integrals with fermionic legs, which
illustrate the general properties.
