  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 cannot 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 $T_{\rm eff}=$ 16000 -- 20000 K. This suggests that the metal
abundances in warmer DAZ white dwarfs may require another explanation.
