Half-Quantum Vortices in Polar Phase of Superfluid He

The magnetic dipole-dipole interaction does not prevent existence of half-quantum vortices in the polar phase of superfluid He which can be stable in uniaxial anisotropic aerogel. Here we discuss this exotic possibility. After developing a phenomenological theory of phase transition from the normal to the polar superfluid state and then to axipolar superfluid state we calculate the NMR properties of such type superfluids at the rest or under rotation when liquid is filled by an array either single quantum or half quantum vortices.