This seems to be related https://www.duolingo.com/comment/26607029 but they discuss different forms. Your word order looks really strange. Maybe possible in colloquial English but I don't think it is possible at all in any standard English. Or it is very marginal, compare the frequency https://books.google.com/ngrams/graph?content=I+yet+have+not%2C+I+have+not+yet I have not yet is 5000x more common than I yet have not.
As a native (US) English speaker, I don't think "yet have not written" would get much use in speech or in writing, at least in the US. "Have not yet written," on the other hand, would be used quite often, although that construction splits the verb. That used to be a bad thing grammatically, but it is becoming more acceptable in these days of loosened standards...