[mrabcx]

The Wikipedia page lists the publication history, https://en.wikipedia.org/wiki/LK-99#Publication_history and the initial paper and patent history go back to 2020.

[m-i-l]

And according to Wikipedia LK-99 was "discovered" back in 1999, hence the name. It isn't clear if it was also first manufactured back then, but assuming it was, 24 years does seem an awfully long time to notice these allegedly simple signs of room temperature super-conductivity (e.g. if you put a magnet near it then it is said to float as per Meissner effect).