  We propose a baryo- and leptogenesis mechanism in which the B-L asymmetry is
produced in the conversion of ordinary leptons into particles of some depleted
hidden sector. In particular, we consider the lepton number violating
reactions, l Higgs -> l' Higgs', \bar{l'} \bar{Higgs'}, mediated by the heavy
Majorana neutrinos N of the seesaw mechanism, where l and Higgs are ordinary
lepton and Higgs doublets and l', Higgs' the ``sterile'' leptons and Higgs.
This mechanism can operate even if the reheat temperature is smaller than the N
Majorana masses, in which case the usual leptogenesis mechanism through N
decays is ineffective. In particular, the reheat tempearture can be as low as
10^9 GeV or less.
