Some packages are not in the default repositories you can install these on a alternative way.
First install the base development tools:
#pacman -S base-devel #pacman -S wget #pacman -S sudo
Go to https://aur.archlinux.org and find you package
Find the tarball, right click it and copy link location
Wget the package (example nemo-fm) and install the package
$cd ~ $wget https://aur.archlinux.org/packages/ne/nemo-fm/nemo-fm.tar.gz $tar xvzf nemo-fm.tar.gz $cd nemo-fm $makepkg -s $sudo pacman -U nemo-fm-1.0.2-1-i686.pkg.tar.xz
Have fun 🙂