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 _ { W } = 32 \pm 5 km s ^ { -1 } , < V _ { 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 .

For the subset of main-sequence stars with extra-solar planets the age-metallicity relation is very similar to that of the total sample , very flat , the main difference being that these stars are mostly metal-rich , [ M / H ] \ga - 0.2 dex .
However , two of these stars have [ M / H ] \sim - 0.6 dex and have been classified as thick-disk stars .
As for the total sample , the range in ages for these stars with extra-solar planetary systems is considerable with a nearly uniform distribution over 3 \la age \la 13 Gyr .