  The EDELWEISS collaboration aims for direct detection of light dark matter
using germanium cryogenic detectors with low threshold phonon sensor
technologies and efficient charge readout designs. We describe here the
development of Ge bolometers equipped with high impedance thermistors based on
a NbxSi1-x TES alloy. High aspect ratio spiral designs allow the TES impedance
to match with JFET or HEMT front-end amplifiers. We detail the behavior of the
superconducting transition properties of these sensors and the detector
optimization in terms of sensitivity to out-of-equilibrium phonons. We report
preliminary results of a 200 g Ge detector that was calibrated using 71Ge
activation by neutrons at the LSM underground laboratory.
