  We discuss the phenomenology of a minimal model for GeV-scale Majorana dark
matter (DM) coupled to the standard model lepton sector via a charged scalar
singlet. The theoretical framework extends the Standard Model by two $SU(2)_L$
singlets: one charged Higgs boson and a singlet right-handed fermion. The
latter plays the role of the DM candidate. We show that there is an
anti-correlation between the spin-independent DM-Nucleus scattering
cross-section ($\sigma_{\rm SI}$) and the DM relic density. We suggest a
scenario that can be tested in both electron-electron and electron-positron
collisions using the production of same-sign charged Higgs pairs and mono-Higgs
in association with right-handed neutrinos.
