CHARGE ORDER AND ONE-DIMENSIONAL PROPERTIES OF YB4AS3

A polarized neutron diffraction experiment gives direct evidence for a charge order in the extremely low-carrier system Yb4As3. Inelastic ne utron scattering experiments on Yb4As3 revealed the existence of low-e nergy spin excitations that are characteristic of a one-dimensional an tiferromagnetic coupling at low temperatures. The results indicate tha t the one-dimensional arrangement of Yb3+ ions caused by the charge or der plays a main role for the heavy-electron behavior in Yb4As3.