Direct observation of 1-dimensional charge order below the first-order "metal-insulator" transition in Yb4As3

Resonant X-ray diffraction results on the Yb LQ absorption edge of Yb4As3 a re reported. The strong enhancement at the absorption edge of reflections o f type 30(3) over bar at temperatures below the first-order phase transitio n is viewed as direct evidence of a 1-dimensional charge order. The quantit ative determination of the charge ordering, which does not follow the struc tural distortion, has direct impact on models describing the unusual electr onic and magnetic properties of this material.