Local structure of YNi2B2C superconductor determined by x-ray-absorption spectroscopy

We have performed Ni K-edge extended x-ray-absorption fine structure measur ements on YNi2B2C superconductor (T-c similar to 15.2 K) in the temperature range 5-220 K. The results show that local structure is distorted from a p erfect I4/mmm crystalline structure expected from diffraction measurements below T-p similar to 60 K. Two different Ni-Ni distances separated by simil ar to 0.09 Angstrom may be extracted at 5 K. We argue that YNi2B2C is inhom ogeneous at the atomic length scale and discuss a possible reason for the o bserved distortions.