I described here the outcome of a summer research project in 2016 with St Andrews undergraduates Horacio Guerra and Šimon Jurina, on power graphs of torsion-free groups. (It took us a while to write it up, for various reasons.)
The paper was published on-line yesterday here, in the Journal of Algebraic Combinatorics.
Congratulations to Horacio and Šimon! They have beaten me: I was already a postgraduate student when my first paper was published.