Scratched the seed a little with a knife. Put in folded wet papertowel in a place at about 22°. After 18h the seed was already open and swiftly transplanted into a small pot with a bit of reused soil which I flushed before and added some Dynomyco.
I prefer to use new light mix for the seeds, but I ran out so flushing some old soil and letting it dry a little was a handy solution.