  Skyrmions, topologically stable spin textures, are of great interest for new
generations of spintronic devices. In general, the stabilization of skyrmions
has been achieved in systems with broken inversion symmetry, where the
asymmetric Dzyaloshinskii-Moriya interaction (DMI) modifies the uniform
magnetic state to a swirling state. Depending on the crystal symmetries, two
distinct types of skyrmions, Bloch and N\'eel types, have been observed
experimentally. Here, we present, the experimental manifestation of a special
type of spin-swirling, namely antiskyrmions, in a family of acentric tetragonal
Heusler compounds with D2d crystal symmetry. A spiral magnetic ground-state,
which propagates in the tetragonal basal plane, is transformed into a skyrmion
lattice-state under magnetic fields applied along the tetragonal axis over a
wide temperature interval. Direct imaging by Lorentz Transmission Electron
Microscopy (LTEM) shows field stabilized antiskyrmion lattices and isolated
antiskyrmions between 100 K and 400 K, and zero-field metastable antiskyrmions
at low temperatures.
