It's possible that your locale is configured improperly; the most likely reason is that, even though the file names are stored in UTF-8, your terminal (I'm guessing Konsole) still expects a legacy ISO-8859-* encoding.
I don't know the rest, but here are a few steps to ensure the basic configuration is correct.
This script may also help.
Edit /etc/locale.gen, ensure that your preferred .UTF-8 locale (e.g. en_US.UTF-8) is uncommented.
(By default, Arch does not enable any locales.)
Run locale-gen to generate the locales, if they haven't been generated yet.
(Currently generated locales are listed by locale -a.)
Edit /etc/locale.conf and add LANG=en_US.UTF-8.
(The LOCALE= variable in /etc/rc.conf does the same thing, but is, in a way, deprecated in favor of locale.conf.)
Log out completely, then log in again, in order to refresh the environment variables.
Run env | egrep '^(LANG|LC_)' | sort to see what locale settings are in your shell's environment.
Run tr \\0 \\n < /proc/$PPID/environ | egrep '^(LANG|LC_)' | sort to see the terminal's environment.
Both commands should return identical output. If not, they both must at least have ".UTF-8" in LANG values. (".UTF-8" and ".utf8" can be considered identical.) Also, neither command should list LC_ALL.