  In this paper, we present low resolution (R=500) near-infrared spectra for
selected and serendipitous sources in six inner in-plane Galactic fields, with
the aim of analysing the stellar content present. From the equivalent widths of
the main features of the K band spectra (the NaI, CaI and CO bandheads) we have
derived the metallicities of the sources by means of the empirical scale
obtained by Ram\'irez et al. (2000) and Frogel et al. (2001) for luminous red
giants.
  Our results show how the mean metallicity of the sample varies with Galactic
longitude. We find two groups of stars, one whose [Fe/H] is similar to the
values obtained for the bulge in other studies (Molla et al. 2000; Schultehis
et al 2003), and a second one with a metallicity similar to that of the inner
parts of the disc (Rocha-Pinto et al. 2006). The relative density of both
groups of stars in our sample varies in a continuous way from the bulge to the
disc. This could hint at the existence of a single component apart from the
disc and bulge, running from l=7 to l=27 and able to transport disc stars
inwards and bulge stars outwards, which could be the Galactic bar that has been
detected in previous works as an overdensity of stars located at those galactic
coordinates (Hammersley et al. 1994, 2000; Picaud et al. 2003).
