Inspired by a question, that unfortunately has been deleted by the OP after getting some hints from me in a comment.
Lacking serifs the Roman numerals in sans serif fonts look sometimes a bit strange. Do you have some ideas for a workaround?
[Tex/LaTex] Roman numerals in sans serif fonts
fontsroman numeralssans-seriftypography
Related Solutions
Relative newcomers to the TeX world are Google's droid fonts, but a package was recently put on CTAN. It has the feature you want for capital I.
\documentclass{article}
\renewcommand*{\familydefault}{\sfdefault}
\usepackage{droid}
\begin{document}
\Huge This is droid sans. I like it.
\end{document}
No swish on i or l, but j does.
I suggest you take a look at Michael Sharpe's mathalfa (the spelling "mathalpha" works too) package. In the package's user guide, the author lists five "hollowed-out" and fourteen [!] "geometric" variants of blackboard-bold fonts. (Note that not all of the underlying fonts are free.) I trust that one or more of the math blackboard board fonts listed and/or made available through the mathalfa package will meet your needs. (I'm afraid I don't have access to German-language math textbooks.)
A big plus of using the mathalfa package is that you can "mix and match" various math alphabets (blackboard bold, caligraphic, curly, script, fraktur, etc) with ease. Excerpting from the README file that comes with the mathalfa package:
This package provides a standard means of setting math alphabets associated with the macros \mathcal, \mathbb, \mathfrak and \mathscr and, where available, their bold counterparts \mathbcal, \mathbbb, \mathbfrak and \mathbscr.
It mostly bypasses the usual fd and sty files used to load these alphabets in order to allow each to be scaled independently and without silently quantizing the sizes.
Best Answer
I would suggest the package
romanbar. This produces Roman numerals with an over- and an underline, and without serifs.The basic command for this is
\Romanbar{⟨arabic number⟩}, this works also with counters inside! You can instead include a Roman numeral, as well. For more abilities see example file of package documentation.An example (note, in KOMA-Script all titles are by default printed in sans serif fonts):
This package is BTW based on egreg’s answer to a question here on TeX.SE: Roman numerals with over- and underline (the OP Stephen is also the package author).