While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly , the inner Galactic bulge ( |b| < 2 \degr ) remains poorly studied , due to heavy interstellar absorption and photometric crowding .
We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES ( ESO/VLT ) facility .
Our spectra cover the wavelength range of 2.0818 – 2.1444 \mu m with the resolution of R \sim 50,000 and have signal-to-noise ratio of 50–100 .
Our stars are located along the bulge minor axis at l = 0 \degr , b = \pm 0 \degr , \pm 1 \degr , \pm 2 \degr and +3 \degr .
Our sample was analysed in a homogeneous way using the most current K-band line list .
We clearly detect a bimodal MDF with a metal-rich peak at \sim + 0.3 dex and a metal-poor peak at \sim - 0.5 dex , and no stars with [ Fe/H ] > +0.6 dex .
The Galactic Center field reveals in contrast a mainly metal-rich population with a mean metallicity of +0.3 dex .
We derived [ Mg/Fe ] and [ Si/Fe ] abundances which are consistent with trends from the outer bulge .
We confirm for the supersolar metallicity stars the decreasing trend in [ Mg/Fe ] and [ Si/Fe ] as expected from chemical evolution models .
With the caveat of a relatively small sample , we do not find significant differences in the chemical abundances between the Northern and the Southern fields , hence the evidence is consistent with symmetry in chemistry between North and South .