(I am trying to convert a document using Greek TTL to Unicode. I have consulted Greek Unicode tables on the Internet but have failed to convert the said character.)
This is the letter
GREEK SMALL LETTER UPSILON WITH PERISPOMENI, U+1FE6.
The perispōmenē/perispomeni accent, literally "circumflex", has two different forms in Greek depending on the font. Some fonts render it like a Latin circumflex,
û. Others render it like a Latin tilde,
ũ. But the meaning is the same either way, and Unicode doesn't distinguish the two.
The phrase is βίοι Ἰησοῦ, literally "lives of Jesus". You seem to have picked up an extra accent mark, too, which is overlapping with the beta at the beginning.