  Star clusters are key to understand the stellar and Galactic evolution. ASCC
123 is a little-studied, nearby and very sparse open cluster. We performed the
first high-resolution spectroscopic study of this cluster in the framework of
the SPA (Stellar Population Astrophysics) project with GIARPS at the TNG. We
observed 17 stars, five of which turned out to be double-lined binaries. Three
of the investigated sources were rejected as members on the basis of astrometry
and lithium content. For the remaining single stars we derived the stellar
parameters, extinction, radial and projected rotational velocities, and
chemical abundances for 21 species with atomic number up to 40. From the
analysis of single main-sequence stars we found an average extinction
$A_V\simeq 0.13$ mag and a median radial velocity of about $-5.6$ km/s. The
average metallicity we found for ASCC 123 is [Fe/H]$\simeq+0.14\pm 0.04$, which
is in line with that expected for its Galactocentric distance. The chemical
composition is compatible with the Galactic trends in the solar neighborhood
within the errors. From the lithium abundance and chromospheric H$\alpha$
emission we found an age similar to that of the Pleiades, which agrees with
that inferred from the Hertzsprung-Russell and color-magnitude diagrams.
