  We report high angular resolution (~0.6''x0.5'' at 1.3mm) observations of the
Class 0 intermediate-mass (IM) protostar NGC 7129--FIRS 2 using the PdBI. Our
observations show the existence of a hot core at the position of the Class 0
object. This is, up to our knowledge, the first IM hot core detected so far.
Interferometric maps of the region in the the continuum at 3mm and 1.3mm and in
the CH3CN 5_k-->4_k, CH3OH 5_kk'-->4_kk', and D2CO 4_04-->3_03 lines are
presented in this paper. Enhanced CH3CN and CH3OH abundances are measured
towards the hot core (X(CH3CN)~7.010^{-9}, X(CH3OH)~3 10^{-8}-- a few 10^{-7}).
While intense D2CO emission is detected towards the hot core, the N2D+ line has
not been detected in our interferometric observations. The different behaviors
of D2CO and N2D+ emissions suggest different formation mechanisms for the two
species and different deuteration processes for H2CO and N2H+ (surface and
gas-phase chemistry, respectively). Finally, the spectrum of the large
bandwidth correlator show a forest of lines at the hot core position revealing
that this object is extraordinarily rich in complex molecules.
