  We study the nuclear (or A) dependence of the coherent eta photoproduction
reaction in a relativistic impulse approximation approach. We use a standard
relativistic parameterization of the elementary amplitude, based on a set of
four Lorentz- and gauge-invariant amplitudes, to calculate the coherent
production cross section from He-4, C-12, and Ca-40. In contrast to
nonrelativistic treatments, our approach maintains the full relativistic
structure of the process. The nuclear structure affects the process through the
ground-state tensor density. This density is sensitive to relativistic effects
and depends on A in a different manner than the vector density used in
nonrelativistic approaches. This peculiar dependence results in He-4 having a
cross section significantly smaller than that of C-12---in contrast to existent
nonrelativistic calculations. Distortion effects are incorporated through an
eta-nucleus optical potential that is computed in a simple ``t rho''
approximation.
