  A class of spatially-flat models with cold dark matter (CDM), a cosmological
constant and a broken-scale-invariant (BSI) steplike primordial (initial)
spectrum of adiabatic perturbations, generated in an exactly solvable
inflationary model where the inflaton potential has a rapid change of its first
derivative at some point, is confronted with existing observational data on
angular fluctuations of the CMB temperature, galaxy clustering and peculiar
velocities of galaxies. If we locate the step in the initial spectrum at k=0.05
h/Mpc, where some feature in the spectrum of Abell clusters of galaxies was
found that could reflect a property of the initial spectrum, and if the large
scales flat plateau of the spectrum is normalized according to the COBE data,
the only remaining parameter of the spectrum is p - the ratio of amplitudes of
the metric perturbations between the small scales and large scales flat
plateaux. Allowed regions in the plane of parameters (Omega=1-Omega_Lambda,
H_0) satisfying all data have been found for p lying in the region (0.8-1.7).
Especially good agreement of the form of the present power spectrum in this
model with the form of the cluster power spectrum is obtained for the inverted
step (p<1, p=0.7-0.8), when the initial spectrum has slightly more power on
small scales.
