Spin-density-wave order controlled by uniaxial stress in CeAuSb₂

The tetragonal heavy-fermion compound CeAuSb₂ (space group P4/nmm) exhibits incommensurate spin-density wave (SDW) order below T_N ≈ 6.5 Kwith the propagation vector q_A = (δ_A,δ_A,1/2). The application of uniaxial stress along the [010] direction induces a sudden change in the resistivity ratio ρ_a/ρ_b at a compressive strain of ε≈−0.5%. Here we use neutron scattering to show that the uniaxial stress induces a first-order transition to a SDW state with a different propagation vector (0,δ_B,1/2) with δ_B=0.25. The magnetic structure of the new (B) phase consists of Ce layers with ordered moments alternating with layers with zero moment stacked along the c axis. The ordered layers have an up-up-down-down configuration along the b axis. This is an unusual situation in which the loss of spatial inversion in a metallic system is driven by the magnetic order. We argue that the change in SDW wave vector leads to Fermi-surface reconstruction and a concomitant change in the transport properties.