  A new metallicity distribution and an age-metallicity relation are presented
for 437 nearby F and G turn-off and sub-giant stars selected from radial
velocity data of Nidever et al. Photometric metallicities are derived from
uvby-H\beta photometry, and the stellar ages from the isochrones of Bergbusch &
VandenBerg as transformed to $uvby$ photometry using the methods of Clem et al.
The X (stellar-population) criterion of Schuster et al., which combines both
kinematic and metallicity information, provides 22 thick-disk stars.
\sigma_{\rm W} = 32 \pm 5 km s^{-1}, <V_{\rm rot}> = 154 \pm 6 km s^{-1} and
<[M/H]> = -0.55 \pm 0.03 dex for these thick-disk stars, which is in agreement
with values from previous studies of the thick disk. \alpha -element abundances
which are available for some of these thick-disk stars show the typical
alpha-element signatures of the thick disk, supporting the classification
procedure based on the $X$ criteria. Both the scatter in metallicity at a given
age and the presence of old, metal-rich stars in the age-metallicity relation
make it difficult to decide whether or not an age-metallicity relation exists
for the older thin-disk stars. For ages greater than 3 Gyr, our results agree
with the other recent studies that there is almost no correlation between age
and metallicity, \Delta ([M/Fe])/\Delta(age) = -0.01 \pm 0.005 dex Gyr^{-1}.
For the 22 thick-disk stars there is a range in ages of 7-8 Gyr, but again
almost no correlation between age and metallicity.
