Induced-Torque Anisotropy in Potassium

We have measured the induced torque on a large number of spherical single crystals of potassium in the geometry employed in magnetoresistance investigations and have observed a large twofold anisotropy for all orientations at 4.2 K. The preferred direction required by this departure from cubic symmetry is a $〈110〉$ axis; which particular $〈110〉$ axis depends on the residual stress in the crystal.