A conjunctive phrase meaning 'not only that, but also' or 'moreover', used to add and emphasize an additional point beyond what was just mentioned.
彼は試験に合格した。そればかりか、クラスで一番の成績だった。
He passed the exam. What's more, he had the top grade in the class.
その店は安い。そればかりか、サービスもとても良い。
That shop is cheap. Besides that, the service is also very good.
彼女は美しい。そればかりか、頭も良くて性格も穏やかだ。
She is beautiful. On top of that, she's smart and has a calm personality.
最近は残業が多い。そればかりか、休みの日も呼び出されることがある。
Lately there has been a lot of overtime. Furthermore, sometimes I'm called in on my days off.