This looks to me like a ligature - I've seen it come up in pronunciation sections before, although print texts may vary in exactly how it looks. I've seen ligatures shown before as a line connecting two letters, or as the two letters pushed together so the lines are touching (as in "Cœur"). In pronunciation, a ligature indicates that the two letters make one combined sound.
Ligatures are covered in UEB 4.3: the ligature indicator (dots 45, 235) is brailled in between the two letters ligatured in print.