SEM Holdings Limited, an investment holding company, engages in the provision of electrical and mechanical (E&M) engineering services in Macau and Hong Kong. The company is involved in the supply, installation, and maintenance of electrical systems for new and existing buildings in the projects of commercial and residential development, hotel and casino development, public properties, and hotel renovation; and trade of electrical cables. The company was founded in 2006 and is headquartered in Chai Wan, Hong Kong. SEM Holdings Limited operates as a subsidiary of Yao Capital Limited.