Package inputenc Error: Unicode character

I had the same error from a reference in a bib file. I left the bib file as is and used DeclareUnicodeCharacter{03B3}{$gamma$} and it worked a treat. Now the $gamma$ comes up nicely!

Glad you solved this. Your options include:

• Load the unicode-math package in a native Unicode engine, such as LuaLaTeX. It will understand all Unicode characters. This is what I would recommend, unless your publisher or professor requires you to use legacy 8-bit fonts.
• Load usepackage[LGR,T1]{inputenc} on a modern distribution, and it should understand γ in text mode. The kernel will only set up the Unicode characters that are in a text encoding that you loaded.
• Do a search-and-replace in your source file.
• Recent versions of babel should be able to automatically switch to a Greek font when they see Greek letters.
• Define a command to display γ (either with inputenc or newunicodechar). This should probably be something like ifmmodegammaelsetextgammafi so it will work in either text or math mode.