pandoc to produce pdf with latex, "paper" document class: missing affiliation and date

I am new to pandoc and latex. I cannot get to have the author affiliation to be part of the final pdf I produce using document class paper.

Let's assume I have the following source.md file:

---
title: my super document
subtitle: blablabla
author:
  - me
  - my friend
  - my other friend
institute: alien space agency
date: <#today>
header-includes:
  - \\usepackage{endnotes}
abstract: |
  This document describes a super research project.
---
start of the writing blablabla...

<#today> is a gpp macro that translates to \today in the tex source.

I use pandoc like this:

cat source.md | gpp -H --include macros.gpp | pandoc -f markdown --variable documentclass=paper --standalone --smart --atx-headers --from=markdown+yaml_metadata_block -o document.pdf

In the produced document.pdf, there is no date and no affiliation for authors. However, if I use document class article I have the correct date. But still no authors institute.

How can I have both date and authors institute with paper document class ?

edit: more info...

If I produce a tex document here is what I get:

\title{my super document}
\providecommand{\subtitle}[1]{}
\subtitle{blablabla}
\author{me \and my friend \and my other friend}
\providecommand{\institute}[1]{}
\institute{alien space agency}
\date{\today}

Which looks ok to me. But there are only authors (without institute) and no date in the final document. I assume it is because of paper document class, changing to article shows the date but no institute...

My pandoc version is 1.19.2.1