$\beta$ and $0\nu\beta\beta$ decays with sterile fermions

Motivated by the capability of the KATRIN experiment to explore the existence of KeV neutrinos in the [1-18.5] KeV mass range, we explore the viability of minimal extensions of the Standard Model involving sterile neutrinos (effectively accounted by the 3+1 framework) and study their possible impact in both the beta decay and the neutrinoless double-beta decay effective mass, for the two possible ordering of the light neutrino spectrum. We also explore how both observables can discriminate between motivated low-scale seesaw realizations involving KeV sterile neutrinos.