それに is a conjunction which adds further information to the preceding sentence. The information before and after それに are similar in speaker attitude(e.g., whether the speaker perceives it to be positive or negative). In other words, what follows それに is positive when the content of the preceding sentence is positive, and what follows それに is negative when the content of the preceding sentence is negative.
わたしは 寒気が します。それに、はき気も します。
I have a chill. Moreover, I feel sick/nauseated.
この スープは おいしいです。それに、えいようも あります。
This soup is delicious. What's more, it's nutritious.