I have read a few posts regarding the placement of Appendix after the References heading on this site but unfortunately none of them is working for me. The following is the YAML that I am using:

---
title: XX
header-includes:
   - \usepackage{soul}
   - \usepackage{xcolor}
   - \usepackage[font=bf]{caption}
author:
  - name: A I
    email: [email protected]
    affiliation: Dta b of Ptan
    correspondingauthor: true
    footnote: 1
  - name: Sa Nem
    email: [email protected]
    affiliation: Se b 
address:
  - code: Ste bk of Pn
    anization: Ste bk of Pn
    addressline: I Chgar ro
    city: Ki
    state: Sh
    country: Pan
footnote:
  - code: 1
    text: "This is first author footnote."
  - text: "This is random footnote by authors."
abstract: |
  We study the he survey finds that while the informal sector is growing in Pakistan, its impact on price rigidity has decreased significantly. 
keywords: 
  - Priiness
  - Priews
  - Surata
  - Excate
journal: "S working paper series"
date: "`r Sys.Date()`"
classoption: preprint, 3p, authoryear
bibliography: mybibfile.bib
biblio-style: apalike
linenumbers: false
urlcolor: blue
numbersections: true
csl: 
output:
  bookdown::pdf_book:
    base_format: rticles::elsevier_article


---

I have used the following methods to get my references above appendices but have failed

Method 1

# References {.unnumbered}

::: {#refs}
:::

# Appendix {.unnumbered}

Method 2

# References {.unnumbered}

<div id="refs"></div>

# Appendix {.unnumbered}

Is there any way I can insert appendices in the same .Rmd file as all my other work and avoid making any extra file for appendices.