Open the brackets. Use full forms.

This year I (to be, not) to South America yet, but in January I went to Australia.​

Можете yet в конце первого формального предложения так и оставить:

This year I have not been to South America yet, but in January I went to Australia.​

А можете его в серединку поставить:

This year I have not yet been to South America, but in January I went to Australia.​