Does Antimatter Fall Up or Down? Scientists Can't Say
livescience.com
livescience.com
So they devised an experiment incapable of deciding that question and then someone came along and made a huge conundrum of the fact that such an experiment doesn’t provide conclusive results.
Really, interactions of single atoms with gravity are extremely difficult to measure, as a single photon from basically anywhere can skew the results massively. Even with very many (single) atoms, it is difficult to distinguish the effect of gravity from the background noise in an experiment as theirs.
However, if general relativity is remotely correct, then antimatter will fall down just as matter does. And so far, everything appears to hint at that being the case.