  In the context of direct searches of sub-GeV Dark Matter particles with
germanium detectors, the EDELWEISS collaboration has tested a new technique to
tag ionizing events using NbSi transition edge athermal phonon sensors. The
emission of the athermal phonons generated by the Neganov-Trofimov-Luke effect
associated with the drift of electrons and holes through the detectors is used
to tag ionization events generated in specific parts of the detector localized
in front of the NbSi sensor and to reject by more than a factor 5 (at 90% C.L.)
the background from heat-only events that dominates the spectrum above 3 keV.
This method is able to improve by a factor 2.8 the previous limit on
spin-independent interactions of 1 GeV/c2 WIMPs obtained with the same detector
and data set but without this tagging technique.
