  The optical spectrum of the infrared source IRAS 04296+3429 (optical
counterpart-G0 Ia star, V=14.2) was obtained with the echelle spectrometer PFES
at the prime focus of the 6 m telescope. We discover emission bands (0,0) and
(0,1) of the Swan system of the C2 molecule in the optical spectrum of IRAS
04296+3429. Comparison with the spectrum of the Hale-Bopp comet leads us to
propose that in both cases the same mechanism (resonance fluorescence) is
responsible for the emission in the C2 molecular bands.
  Several strong absorption features whose positions coincide with known
diffuse interstellar bands are revealed in the spectrum of IRAS 04296+3429.
  The infrared spectrum of IRAS 04296+3429 shows the famous 21 um feature, but
this object has not been observed by KAO. However, like IRAS 05113+1347, IRAS
05341+0852 and IRAS 22223+4327, our detailed modelling of its spectral energy
distribution suggested that this source also should show the 30 um band. In
fact, ISO discovered a broad, relatively strong feature around 30 um for IRAS
04296+3429.
  The surface chemical composition of the source IRAS 04296+3429 is
metal-deficient (the averaged value of the abundances of the iron group
elements Ti, V, Cr and Fe relative to the solar values is [M/H]=-0.9 and has
been considerably altered during the evolution: carbon, nitrogen and s-process
elements are overabundant relative to the metallicity.
  The totality of physical and chemical parameters derived for IRAS 04296+3429
confirms a relation between presence of the feature at 21 um in the spectrum of
a carbon rich star and an excess of the s-process elements.
