  We report the discovery of 56 new Lyman-alpha-emitting candidates (LECs) at
redshift z=2.5 in a field of 8'x14' around two previously known weak radio QSOs
and a cosmic microwave background decrement (CMBD) that is plausibly due to the
Sunyaev-Zel'dovich effect. Broad-band and medium-band imaging at the redshifted
Lyman-alpha wavelength have allowed us to identify the LECs at the redshift of
the QSOs. Three of the brightest LECs have been confirmed spectroscopically,
with redshifts between z=2.501 and z=2.557; one of them is another QSO.
Excluding the third QSO, the four spectroscopically confirmed objects form a 3'
filament with a rest-frame velocity dispersion of 1000 km/s lying adjacent to
the CMBD, and there is a significant concentration of LECs at the NW end of the
filament around the brightest QSO. If confirmed, a velocity dispersion ~1000
km/s on a proper scale ~1 Mpc at redshift z=2.5 would, in and of itself,
constrain the cosmological model to low Omega.
