[en] Narrow peak structures at proportional300 keV have been observed in the positron spectra of supercritical collision systems. There remains only little possibility that these structures can be associated with nuclear deexcitation of the separated collision products. Emitted from systems both existing for >10^-20 sec and apparently moving with the velocity of the center of mass these positrons may represent candidates for the process of spontaneous positron emission from metastable di-nuclear quasiatoms although straight-forward scaling of supercritical binding with the combined charge of the colliding nuclei does not agree with the observed energies. (orig.)