Грамматика русского языка. Часть 7. Имя прилагательное. Глава 13. Сравнительная степень: конструкции. Russian Grammar. Part 7. The Adjective. Unit 13. The Comparative. Constructions.

In English you form the second part of the comparative by using the word than (he has a more beautiful car than you). In Russian this part of the sentence is formed either by using the word чем (than) or by using the genitive.

When we are using the long form comparative in Russian, we must form the second part of the comparative by using the word чем:

У него более красивый автомобиль, чем у тебя.
He has a more beautiful car thаn you.