A Hebrew accent mark. There is an atnah in each of verse of the Hebrew Bible. It roughly divides the verse into two halves. Notice the carrot like symbol under the tav. See KHW p. 69.
עֲשִׂיתֶ֑ם
Words that have either an atnah, silluq, or zaqef-qaton are said to be in pause. More here and a complete list here.
