We present near-infrared spectroscopic observations of 20 previously known DAZ white dwarfs obtained at the NASA Infrared Telescope Facility .
Two of these white dwarfs ( G29-38 and GD362 ) are known to display significant K-band excesses due to circumstellar debris disks .
Here we report the discovery of excess K-band radiation from another DAZ white dwarf , WD0408-041 ( GD56 ) .
Using spectroscopic observations , we show that the excess radiation can not be explained by a stellar or substellar companion , and is likely to be caused by a warm debris disk .
Our observations strengthen the connection between the debris disk phenomena and the observed metal abundances in cool DAZ white dwarfs .
However , we do not find any excess infrared emission from the most metal rich DAZs with T _ { eff } = 16000 – 20000 K. This suggests that the metal abundances in warmer DAZ white dwarfs may require another explanation .