In a letter to Tendulkar, Singh described him as a "true ambassador" of India in the world of sports.
"In conferring this award on you, the nation has honoured a living legend whose numerous achievements and exemplary conduct on the cricketing field have inspired millions across the globe. You have been a true ambassador of India in the world of sports. We salute you as a sporting genius and a global sporting icon," Singh said.
In his congratulatory letter to Rao, Singh lauded his efforts of "passionately nurturing" young scientists.
"In conferring this award on you, the nation has honoured an eminent scientist and a well recognised international authority on solid state and materials chemistry. We salute your work not only as a scientist but also in passionately nurturing young scientists and strengthening the science infrastructure in our country," the PM wrote.
He said India looks forward to his continued guidance of Indian science and scientists.