  We present results on dielectron production in Ar+KCl collisions at 1.76A
GeV. For the first time $\omega$ mesons could be reconstructed in a heavy-ion
reaction at a bombarding energy which is well below the production threshold in
free nucleon-nucleon collisions. The omega multiplicity has been extracted and
compared to the yields of other particles, in particular of the phi meson. At
intermediate e+e- invariant masses, we find a strong enhancement of the pair
yield over a reference spectrum from elementary nucleon-nucleon reactions
suggesting the onset of non-trivial effects of the nuclear medium.
Transverse-mass spectra and angular distributions have been reconstructed in
three invariant mass bins. In the former unexpectedly large slopes are found
for high-mass pairs. The latter, in particular the helicity-angle
distributions, are largely consistent with expectations for a pair cocktail
dominated at intermediate masses by delta Dalitz decays.
