Better to make it a function like this as aliases don't have support for positional parameters like $1, $2
etc:
txz() {
of="$1"
nf="$of"$(date -I)
mv "$of" "$nf"
tar cJvf "$nf.txz" "$nf" --remove-files
}
Or to make in one line:
txz() { of="$1"; nf="$of"$(date -I); mv "$of" "$nf"; tar cJvf "$nf.txz" "$nf" --remove-files; }