  In a previous work [arXiv1905.01121] we have derived a quantum master
equation for the dynamics of a scalar bosonic particle interacting with a weak,
stochastic and classical gravitational field. As standard matter is made of
fermions, such an equation should be suitably extended to describe more
relevant experimental situations. Here we derive a non relativistic model for
the gravitational decoherence of spin 1/2 particles. We enrich the treatment by
considering also a coupling with an external classical electromagnetic field.
We comment on the differences with the scalar bosonic model and we describe the
regimes in which they become negligible.
