A form of である with the topic particle は added; used to acknowledge or assert something while contrasting or limiting it (often somewhat formal or emphatic).
彼は経験が浅いではあるが、学ぶ意欲は強い。
Although he has little experience, his willingness to learn is strong.
確かに高価ではあるが、この品質なら納得できる。
It's certainly expensive, but given the quality I can accept it.
その方法は古いではあるが、今でも有効な場合がある。
That method may be old, but it can still be effective in some cases.