[Groff] Help with umlauts

[Bates, Rod]

I have an old input file and its corresponding .ps file, both of
which came to me from long ago and far away.  I can get groff 
to regenerate the .ps, except it complains about a few occurrences
of umlauted characters.  For example, in the input file, there
is a \*U which shows as capital U with umlaut in the original
.ps file.  Using groff, I get the message: 

warning: can't find special character `U:' 

on this line, and the output .ps file just has the umlauted U
omitted altogether.  

The input file has a comment:

.\" use: pic | tbl | eqn | ditroff -me

I am using: 

groff -pte -me

What do I need to do to get these characters?