Use encoding="UTF-8" in rio

Question

Some of my students got an issue yesterday. I tried to solve it with some code examples from Stackoverflow, but none of them worked for me.

I tried to import an .xlsx file and some of the characters like "ü" got replaced by "". It seems that this is an encoding problem, so I tried the following:

library(rio)    
df <- import("example.xlsx",encoding = "UTF-8", na="...")

R throws back this error:

unused argument (encoding = "UTF-8 ")

I have to use the Rio package! So does anybody has a solution for my problem? It seems that this problem mostly appears on Mac computers with OSX.

I really appreciate your help, thanks a lot!