invalid utf-8 sequence error from .bib file despite valid character in main document

Question

I'm working on a paper main.tex with a separate Bibtex file references.bib. I compile with:

lualatex main
bibtex main
lualatex main

(Note that I must use bibtex because the journal style is not compatible with biber)

In the last step 'lualatex main', I obtain the error String contains an invalid utf-8 sequence which comes from a reference in the Bibtex file: one of the authors names starts with character Á (the error does not happen if this character is removed).

I'm confused: the character seems to be valid utf-8, and it prints without any issue if it's inside the main document. Additionally my Bibtex file contains other uncommon accentuated characters which are displayed normally in the pdf.

What am I missing?

Sorry, I omitted to show the offending entry in the bibtex file:

@book {walsh15,
      author = {Walsh, Kieran and Carney, Gemma M. and Ní Léime, Áine},
      title = "Ageing through Austerity: Critical Perspectives from Ireland",
      year = "2015",
      publisher = "Policy Press",
      address = "Bristol, UK",
      isbn = "9781447316251",
      doi = "10.51952/9781447316251",
      url = "https://bristoluniversitypressdigital.com/view/book/9781447316251/9781447316251.xml"
}

and the resulting .bbl entry:

%Type = Book
\bibitem[{Walsh et~al.(2015)Walsh, Carney and Ní~Léime}]{walsh15}
\bibinfo{author}{Walsh, K.}, \bibinfo{author}{Carney, G.M.},
  \bibinfo{author}{Ní~Léime, \C3.}, \bibinfo{year}{2015}.
\newblock \bibinfo{title}{Ageing through Austerity: Critical Perspectives from
  Ireland}.
\newblock \bibinfo{publisher}{Policy Press}, \bibinfo{address}{Bristol, UK}.
\newblock \URLprefix
  \url{https://bristoluniversitypressdigital.com/view/book/9781447316251/9781447316251.xml},
  \DOIprefix\doi{10.51952/9781447316251}.

And here is the error message:

! String contains an invalid utf-8 sequence.
l.362   \bibinfo{author}{Ní~Léime, 
                                   �..}, \bibinfo{year}{2015}.

hard to say with no code shown. The most common reason for getting that error is the file does in fact have an incorrectly encoded character. — David Carlisle, Feb 23 '24 at 15:49
show at least the generated bbl for that entry and the full error from the log which will show the error context — David Carlisle, Feb 23 '24 at 15:52
See pages 3-4 in http://mirrors.ctan.org/biblio/bibtex/base/btxdoc.pdf — hair-splitter, Feb 23 '24 at 15:55
My guess is you have an Á in some place that BibTeX is doing case changing or similar: that will go wrong and the output is then likely invalid - but like @DavidCarlisle says, we need an example — Joseph Wright, Feb 23 '24 at 15:59
bibtex doesn't like utf8 at the begin of name. It tries to split it for the initial. — Ulrike Fischer, Feb 23 '24 at 16:13
For more information on how to enter "accented" characters in a bib file, please see How to write “ä” and other umlauts and accented letters in bibliography? — Mico, Feb 23 '24 at 18:58

score 4 · Accepted Answer · answered Feb 23 '24 at 18:54

bibtex knows nothing about multi-byte encodings so while trying to fine the "Inital letter" of the name it pulls out just one byte of the bytes for Á so ends up with an invalid generated latex .bbl file. {\'A} is the documented bibtex syntax, and keeps everything ascii.

score 3 · Answer 2 · answered Feb 23 '24 at 19:07

If you don't want to replace accented characters in the bibliography, I suggest you run bibtexu -- where "u" denotes either unicode or utf8 -- instead of "plain" bibtex.

\documentclass{article}
\begin{filecontents}[overwrite]{mwe.bib}
@book{walsh15,
      author = {Walsh, Kieran and Carney, Gemma M. and Ní Léime, Áine},
      title = "Ageing through Austerity: Critical Perspectives from Ireland",
      year = "2015",
      publisher = "Policy Press",
      address = "Bristol, UK",
      isbn = "9781447316251",
      doi = "10.51952/9781447316251",
      url = "https://bristoluniversitypressdigital.com/view/book/9781447316251/9781447316251.xml"
}
\end{filecontents}
\usepackage[numbers]{natbib}
\bibliographystyle{plainnat}
\usepackage{xurl}
\begin{document}
\cite{walsh15}
\bibliography{mwe}
\end{document}

I tested bibtexu for the companion and found to many bugs to include it. — Ulrike Fischer, Feb 24 '24 at 00:29
@UlrikeFischer - It's a real pity that bibtexu isn't up to snuff in terms of bugginess. — Mico, Feb 24 '24 at 12:01

invalid utf-8 sequence error from .bib file despite valid character in main document

2 Answers2