SED: how to remove newline after pattern?

Hi,
I have the following XML not well-indented code:

<hallo
>this is a line
</hallo>

So I need to remove the newline.

This syntax finds what I need to correct, but I don't know how to remove the newline after my pattern:

sed 's/<.*[^>]$/&/'

How can I subtract the newline after my pattern, please?

Thank you in advance,
Nico

I'm not sure which format you want, but one of these should do what you are looking for:

sed -e '/<[^>][^>]*/N' -e 's/\n>/>\n/'

sed -e '/<[^>][^>]*/N' -e 's/\n//'