Normally au-devant de (with an hyphen) means something like “coming toward” (French à la rencontre de), but Grevisse (Le Bon Usage, 14r ed., §1073(a)1°) notes that the meaning “in front of” is also found and listed in the Trésor de la langue Française (here, in the subs. masc. entry, under sense C) but not in the Robert or the Academie’s dictionary, and calls it “rare”, that is also my feeling: strongly literary (as such rare usages tend to sound).