  A search is described for the generic process e+e- to X Y, where X is a
neutral heavy scalar boson decaying into a pair of photons, and Y is a neutral
heavy boson (scalar or vector) decaying into a fermion pair. The search is
motivated mainly by the cases where either X, or both X and Y, are Higgs
bosons. In particular, we investigate the case where X is the Standard Model
Higgs boson and Y the Z0 boson. Other models with enhanced Higgs boson decay
couplings to photon pairs are also considered. The present search combines the
data set collected by the OPAL collaboration at 189 GeV collider energy, having
an integrated luminosity of 182.6pb-1, with data samples collected at lower
energies. The search results have been used to put 95% confidence level bounds,
as functions of the mass of X, on the product of the cross-section and the
relevant branching ratios, both in a model independent manner and for the
particular models considered.
