Bigger font size in hyperlink column in a list via JSON

I would like to make an alternative text in a hyperlink column bigger.

In a title column, it works fine with this code:

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "a",
  "txtContent": "@currentField",
  "style": {
    "font-size": "13pt"
  }
}

But when I paste this into hyperlink column, it does nothing or the column is broken.

My hypothesis is that the elmType is set wrong.

Anyone know how to solve it?
Thanks.