Complex sentence: In the 1906--07 season, Lehman was signed as free agent by the Canadian Soo of the International Professional Hockey League (IPHL); the IPHL was the first fully professional ice hockey league.
Split into simpler sentences: In the 1906--07 season, Lehman was signed as free agent by the Canadian Soo of the International Professional Hockey League (IPHL). The IPHL was the first fully professional ice hockey league.