ABSTRACT: A Dirac field of negative energy is introduced. It is shown how such a negative energy field is connected to the Dirac field of positive energy. We also show that electric charges of the negative energy field are exactly opposite to those of the positive energy field. Finally we show, within the framework of QFT, how a fermion with a positive energy and mass state can be transformed into a fermion whose energy and mass state is negative – and vice versa – through the use of an electromagnetic potential. This gives another possible explanation for the excess of antiprotons observed in the AMS-02 experiment in 2016, as a primordial antimatter incursion.