As a standard, bibtex is used as a citation-renderer in Pandoc’s Markdown, that is, in RMarkdown as well. bibtex is useful for a fair amount of citation task, but biblatex allows for a finer control. For instance, multiple bibliographies for one document are possible. For instance, citing a newspaper article using bibtex left me scratching my head, as I wanted to have the exact day of the date (not only the year) …