Kondo effect in the presence of spin-orbit coupling

We study the $T=0$ Kondo physics of a spin-$1/2$ impurity in a noncentrosymmetric metal with spin-orbit interaction. Within a simple variational approach we compute ground-state properties of the system for an arbitrary form of spin-orbit coupling consistent with the crystal symmetry. This coupling produces an unscreened impurity magnetic moment and can lead to a significant change of the Kondo energy. We discuss implications of this finding both for dilute impurities and for heavy-fermion materials without inversion symmetry.