  Age-metallicity relation for the Galactic disc is a crucial tool and to
constrain the Galactic chemical evolution models. We investigate the
age-metallicity relation of the Galactic disc using the red giant branch stars
in the Solar neighbourhood. The data cover the Galactocentric radius of $7\leq
R_{\rm gc} (\rm kpc) \leq9.5$, but extends up to 4 kpc in height from the
Galactic plane. We use kinematic age derived from highly precise astrometric
data of Gaia Data Release 2 and element abundance ratios from high-resolution
spectroscopic data of APOGEE-2 catalogues. We apply a two-component Gaussian
mixture model to chemically separate the programme stars into thin and thick
disc populations. The stars in each population are grouped into different
distance intervals from the Galactic plane. The mean metal abundances and
velocity dispersions of the stars in the groups were calculated and the
kinematic ages were determined from their kinematic parameters. We found a
steep relation for the thin disc with -0.057$\pm$0.007 dex Gyr$^{-1}$, and even
a steeper value of -0.103$\pm$0.009 dex Gyr$^{-1}$ for the thick disc. These
age-metallicity relations along with the prominent differences in age,
metallicity, and kinematic behaviours seen from the data, clearly show it is
important to consider the distinct formation scenarios of the Galactic disc
components in modelling the Milky Way.
