  We have developed a detector, consisting of a cryogenic calorimeter with a
scintillating crystal as absorber, and a second calorimeter for the detection
of the scintillation light, both operated at 12 mK. Using a CaWO4 crystal with
a mass of 6g as scintillating absorber, we have achieved a discrimination of
nuclear recoils against electron recoils with a suppression factor of 99.7% at
energies above 15 keV. This novel method will be applied for background
rejection in the CRESST (Cryogenic Rare Event Search with Superconducting
Thermometers) experiment looking for dark matter Weakly Interacting Massive
Particles (WIMPs).
