Union Berlin have signed Croatian striker Ivan Prtajin from Wehen Wiesbaden, the Bundesliga side said on Thursday. The 28-year-old was relegated to the third tier with Wiesbaden in the season just finished but now finds himself in the German top flight. “We’re getting a highly sought-after, robust striker who is good in the air and has strong running ability. He wants to prove himself in the Bundesliga and will be good for our goal threat and flexibility up front,” Oliver Ruhnert, Union’s managing director for football said in a statement. No details were given regarding the duration of the co…