  We demonstrate a simple way to achieve superdirectivity of electrically small
antennas based on a spherical dielectric particle with a notch. We predict this
effect theoretically for nanoantennas excited by a point-like emitter located
in the notch, and then confirm it experimentally at microwaves for a ceramic
sphere excited by a small wire dipole. We explain the effect of
superdirectivity by the resonant excitation of high-order multipole modes of
electric and magnetic fields which are usually negligible for small perfect
spherical particles.
