  The interplay of crystal symmetry, magnetism, band topology and electronic
correlation can be the origin of quantum phase transitions in condensed matter.
Particularly, square-lattice materials have been serving as a versatile
platform to study the rich phenomena resulting from that interplay. In this
work, we report a detailed magnetic study on the square-lattice based magnetic
topological semimetals GdSb_{x}Te_{2-x-{\delta}}. We report the H-T magnetic
phase diagrams along three crystallographic orientations and show that, for
those materials where a charge density wave distortion is known to exist, many
different magnetic phases are identified. In addition, the data provides a clue
to the existence of an antiferromagnetic skyrmion phase, which has been
theoretically predicted but not experimentally confirmed in a bulk material
yet.
