He has also appeared in contemporary operas, as Jesus in Jonathan Harvey's Passion and Resurrection and as Amfortas in Mea culpa by Christoph Schlingensief.
Haumer has sung under the direction of Gustavo Dudamel, Ivor Bolton, Jesús López Cobos, Fabio Luisi, Peter Schreier, Kristjan Järvi, Sylvain Cambreling, Martin Haselböck and Erwin Ortner.
Performances in the most important European concert halls and festivals such as the Cité de la musique (Paris), Auditorio Nacional in Madrid, National Philharmonic in Warsaw, Dresden Philharmonic, Festival Oude Muziek in Utrecht, Theater an der Wien, Wiener Festwochen, Wiener Musikverein, Konzerthaus, Vienna, Styriarte Graz and Carinthian Summer [de].
[3] In 2016 and 2017, he performed as soloist at the gala "Christmas in Vienna" alongside Juan Diego Flórez, Anne Sofie von Otter and Olga Peretyatko.
[4][5] Numerous CD and DVD recordings on labels such as Deutsche Grammophon, Hyperion, cpo as well as radio and television broadcasts have been issued.