Science

I have no idea what would happen if you split one or even how youd "split" one(without ramming it into a high energy partical and letting it then decay, but thats just fusion with extra steps) but if you fused two youd get an antihelium particle. It would behave functionally identically to a regular helium atom except with opposite charge. I believe fusing two hydrogen gives you a loghtly positively charged helium, so fusing two antihydrogen would give you a slightly negative antihelium.

Fun fact, antiparticles are literally the same thing as a regular particle with its CPT symmetries reversed. You you can take a particle, swap its charge, swap its partity(or handedness, its the difference between what you look like and what you look like in a mirror, but its for quantum spin which doesnt really mesh well with our understanding of 3d space) and then swap its direction of travel through time and youre literally just looking at what looks to be an antiparticle.