That probably isn't halogen lighting because halogen is an incandescent source with halogen gas added to reduce emissions from the heated filament being deposited on the glass. Incandescent lamps have far too much thermal lag to flicker which is why they are a nice light source but they are generally far too inefficient for lighting large sports venues. So you are dealing with either a discharge type lamp (sodium most likely) or newer LED lighting.
Setting to auto white priority is probably going to give you the best results for the JPG files you need instantly. In a setting like this, the camera can generally find something white and set color temperature based upon it. With RAW files you can change color temperature in post but with JPG files you need immediately, auto white priority will probably provide the most consistent color temperature match.
Flicker at 50hz would occur in Europe and some other parts of the world, if you are shooting in North America the line frequency is 60hz. BUT with a lot of newer lighting, flicker is no longer tied to the line frequency nor is it even stable so you can end up with multiple flicker rates across an arena that are all constantly changing and this impacts both color temperature and exposure. I have shot on football fields where the white balance is radically different over small sections of the same field and with the newer lighting with lots of additional controls including the goofy "celebration" modes, it isn't going to get any better.
Most of the stuff can be fixed in post pretty easily but that doesn't help with the images that need immediate upload. So give auto white priority a try and see if that improves the percentage of good captures.
I have never been a fan of anti-flicker because it does impact burst rate and it wasn't infallible even with old school high intensity discharge lighting that flickered at a stable line rate.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
