  Magnetic skyrmions are particle-like spin-swirling objects ubiquitously
realized in magnets. They are topologically stable chiral kinks composed of
multiple modulation waves of spiral spin structures, where the helicity of each
spiral is usually selected by antisymmetric exchange interactions in
noncentrosymmetric crystals. We report an experimental observation of a
distorted triangular lattice of skyrmions in the polar tetragonal magnet
EuNiGe$_3$, reflecting a strong coupling with the lattice. Moreover, through
resonant x-ray diffraction, we find that the magnetic helicity of the original
spiral at zero field is reversed when the skyrmion lattice is formed in a
magnetic field. This means that the energy gain provided by the skyrmion
lattice formation is larger than the antisymmetric exchange interaction. Our
findings will lead us to a further understanding of emergent magnetic states.
